The ultimate decision regarding voiding your warranty is Ducati's but if you read your warranty you'll see that Ducati's warranty is not predicated upon an authorized dealer performing all of your maintenance work nor does it require that the motorcycle remain in an unmodified condition or contain only factory parts during the warranty period.
However, if you have a claim during the warranty period it's reasonable for Ducati to suspect that inadequate maintenance and/or aftermarket parts had contributed to the failure. But legally they can't just void your entire warranty. They have to prove that the presence of non-factory parts or improper maintenance caused or contributed to the failure.
Conversely, there is an obligation and need that you keep records and receipts that can demonstrate that any maintenance work not performed by Ducati was done according to the service schedule and all replacement fluids met Ducati's specification.
To avoid any concerns, any performance parts that you install have to meet Ducati's specification as well. The only parts that meet this criteria are Ducati Performance parts and they have to be installed by an authorized dealer for the parts themselves to be covered under warranty and to avoid warranty issues on the motorcycle itself.
Consequently, if you decide to install any non-Ducati part or use a non-approved lubricant, fuel, or hydraulic fluid and you experience a related failure, expect a warranty challenge on a case-by-case basis. If you change your oil and filter yourself and later have an engine seizure determined by Ducati to be the result of inadequate lubrication you've got a problem.
So, even though a dealer cannot say that your entire warranty is void due to aftermarket pipes, you'll loose if you have an engine failure that can be traced to an excessively lean fuel condition caused by installing an incorrect Eprom for example.
Aftermarket parts usually carry their own warranty and often are of higher quality than OEM parts but still can cause problems if improperly installed, and it may be unwise to substitute a part (say a filter) simply because it's less expensive than the OEM unit.
Regarding the rocker replacement.
Ducati has known of this design deficiency since it first appeared in 1996. On bikes with 4-valve heads, the rocker arms have simply not been reliable. A good number of them flake-off their chrome plating before the time of their first service at 6,000 miles and that often can result in scratched camshaft lobes if not caught in time. The rocker arms in 851/888's and pre-1996 916's typically lasted 80K miles with no problems. 1996 was the year when Ducati began to outsource the rocker plating to subcontractors and problems began.
Ducati basically concedes that there has indeed been a rocker problem in the past, but has repeatedly assured us that things have been fixed. They also point out that the rocker problem will be covered under warranty, even if you're outside the warranty period, (if it's not a race bike or an SPS/R.) So, when you have this problem, just work with your local dealer who will replace the damaged parts. If you're out of warranty, you usually will have to pay for the labor cost only.
They're not just being good guys here. From a legal standpoint, if there is a known manufacturing defect, warranty period or not, the manufacturer is responsible to sell you goods that can perform up to the standard expected when purchased - no matter how long after purchase.
There probably have been 17 rocker design iterations over the years. For 2001, Ducati announced they were now using an improved rocker design that is also compatible with earlier year engines. The new 2001 opening rockers can be identified by a small dot punched on the side where they fit onto the shaft. Unfortunately these rockers fail in exactly the same way. So even if you have a 2001 or later model, make sure that when you have your bike serviced at 6K miles, that they remove the cams (25 minutes labor) and inspect the rockers since any damage cannot be seen otherwise. The flaking starts as small little patches and if you catch early you can avoid cam damage.
To play it safe, and to make sure that Ducati doesn't balk at replacing your rockers, it's a good idea to keep adequate records to show that you've adjusting the engine valve clearances to Ducati specs on schedule, and used a lubricant that conforms to Ducati's specification in the owners manual.*There have been instances reported where some Ducati dealers have tried to make the owner feel that they have somehow abused the bike and then charged them for repairs.
The rocker arms have a hard chrome coating to increase their wear resistance where they contact the cam lobe. The opening rockers are more likely to be affected but occasionally the closing rockers flake as well. The closers don't take anywhere near the abuse as the openers.
There has been a lot of debate about the reasons why the chrome comes off. The answer is likely a combination of inadequate chrome thickness and the unusually long time needed for the oil to reach these parts during a cold start. In normal circumstances, a good synthetic oil would leave a surface film that is adequate lubrication until oil flow is established.
There's some correlation between a lack of oil and rocker failures. For example, the horizontal cylinder exhaust rockers sit in a oil bath and rarely fail. Most often, failures are seen in the more distant vertical cylinder rockers, especially on the hotter exhaust side. For the 1999 model year, Ducati increased the size of the oil galleys to the heads to try to solve the problem.
I don't think Ducati knows the definitive answer. If they did, the problem would’ve been corrected years ago. If it's any consolation, this type of problem is not unique to Ducati. Other manufacturers have had rocker hard coating issues in the past. Honda, Kawasaki and Suzuki, to name a few.
Replacing a failed rocker with another having the same potential for failure doesn't make a lot of sense, so some owners have installed Megacycle rockers, stock rocker arms that have been machined down in thickness to allow for a greater thickness of chrome to be applied. Others say that the Corsa rockers are the ultimate fix.
The Megacycle fix is to grind the rocker/cam contact area back .035 to .040 inches and then build back up with a hard nickle-chrome boron alloy brazed onto the rocker, then grind the repair back to factory specs.
http://www.megacyclecams.com/ See Neil Spalding's articles on the Signa Performance website for more information:
http://www.sigmaperformance.com/rockers.html
12-Feb-2004, 19:11 
when our local trading standards gave me the info I quoted above.
Shazaam!
Linear Mode
