My friend only has a cai/tunner and magnaflow cat backs..

And his sensors... Both down and up seem to have problems... the ones under the hood is changed and is now good... he recently changed the ones that are under the car. The car performed really great I mean REALLY REALLY great...

but later that night in the same day a 300c and even a nissan maxima ( turbo ) smoked him ... what could be the problem ?

he says the car just doesnt give full power now ...


and also before he changed the sensors, the rpm was bouncing up and down alwaays ... so after he changed the under sensors its gone... ( im not sure if its back now .. ) Could it be the tune ?

His tune is from sct ( cai/filter... and a headers ) tune... I ordered evo performance tune for him at the beggining .. but he just didnt listen to me.. he took it to a friend and they lost the evo performance tune and got another one from sct ( the one that is free )