Stu, I have read a few times that our Vipers really do not "fully" break in (loosen up) untill we get 7500 to 15,000 miles on them. I have 6300 on mine, and I just came home from a nice ride. I told my son that I can actually feel the Viper getting stronger, as I put more miles on her. She pulls real strong on the top end....say 3rd. gear going 75 mph..yeehaw. The Belangers made a nice improvement there.
As far as 90,000 miles...that is a tough question to answer...it all depends on how the car was cared for...was it maintained properly? And was it driven normally? If it was hammered all the time to 90K..(oil consumption)well ..you will probably be needing an overhaul. Lot of factors weigh in here.
Dave