I had only snorkel mod and samco IC hoses and was running 14.6 quarter mile times pretty consistant.. I got the greddy evo cat-back .. re-set ECU and now a times arent consistant at all and it 3/10 to 1/2 a second slower.... My 60 foot times are always at about 2..... so my launch is the same but the 1/4 is slower... I have ran the car on 2 differnt nights with the new exhaust with the same results.... Any advice?....Also who still thinks snorkel mod is a bad thing? I am thinking of changing it back to stock and running it then

 

I highly doubt the cat-back slowed you down in the 1/4 as most people dyno an increase in hp w/ it.. .its possible that your reset of the ECU (which was not needed when changing the catback) has caused your car to go on a learning process again of fuel and timing and just isnt to the point of where it was before yet....

And a few 10's of a second is most likely caused by weather or driver... your car will run slower in hot &/or humid weather (less dense air)... And 14.6 implies that you probably could work on your launch and shift some more.

 

Launch had the same 60 foot times so launch is ok. Tried it once before I reset the ECU.. had bad times.. Reset the ECU and got the times from last night.. drove the car 4 to 500 miles after reset.