im going the full decat route on my classic then going for a remap when it comes to mot and i put a cat back in will it still run the same even tho the car is mapped to the decats eg lumpy runing and normal emisions

 

depedns what ecu and year of the car.

01 onwards on original ecu given a couple of miles should adjust the idle and cruise enough to pass emissions with cat reinstalled if mapped without, assuming both lambda sensors are fitted and working and it is mapped correctly.

Simon

 

its a my99 uk turbo 2000 car