When my car was in for service several months ago, the dealer re-programmed the factory chip with a flash upgrade (this was the factory recall). Since then, it seems the performance level has gone down, as has the gas mileage, a LOT: ~13cty/20hwy.
I'm planning on a JC chip upgrade, but worry that I should FIRST get the leakdown test and have the O2 sensors checked. Am I missing any possibilities for drop in performance and mpg?
The car has 40k miles on it and has had no other problems. I've been driving it with 92 octane.
'95 540 6-speed