i have my car tuned to a 12.5 a/f ratio @wot...
(5psi of boost) w/ a stock 98 prelude exhaust...

if a bolt on a 3in catback...aprox. how much leaner will my a/f become??

+1 point? 13.5? ...+2points??14.5?

i know the only true way to find out is the dyno...but the closest dyno shop around where i live thinks that for some reason i should be around 13.5 to 14 under boost...(domestic tune shop)

so i am a little weary of going back...but until i find a reputible shop..i was just wondering if it would really be that big of a deal