I thought about doing this to my 996S
... but after visiting Sigma Performance I was persaded not to. I fitted 50mm carbon race cans and the UM239 chip. This made loads of difference across the range. Rideablity was much improved.
I guess you've read the stuff on the Ultimap web site about 12 deg advance etc. Their claims are greater mid range but I find that I've got plenty already.
If you do get this done please let me know.