50mm D&D\'s...
 

...on a 996 bip. Will it scrape though at Donny with a 98db limit?

What do you mean by D&D's?

If D&Ds are aftermarket pipes (excuse my ignorance!) then No...Donny quiet days are very strict and you will struggle to get a standard Duke through let alone with after market pipes on.

Don't know what your noise limits are, but I had a D&D half system (45/50mm) on my 748, and they were obnoxious! Set off car alarms everywhere...