[phrenetiK]

bought a used 135i with full bolt ons and a jb4. dp, midpipe, axleback, and dual cone intake. car is SLOWER THAN STOCK with all these mods. didn't find this rut until i raced and drove a stock 135i.

getting some lambda codes, i replaced o2 sensors, and spark plugs. nothing helped. then i had the idea to take off the jb4.

boom instantly the car was running great. no more rough idle, boosted correctly, pulled hard and instant torque. that led me to believe the jb4 was screwed up. then we installed the jb4 on my friends stock 135i. it turned his car into a MONSTER. my car should even pull harder than it does with all my supporting mods, however that was not the case. we put the jb4 back on my car and same thing. starts idling rough, only boosts to 3psi 1st 5 psi 2nd, 9 psi 3rd...so slow. also throws more lambda codes. take off the jb4 again and bam instantly making over stock performance.

i have no idea whats wrong but would like to testsomething like a cobb or procede on the car and see if they both cause the car to run shitty too, or if my car strangely just hates the jb4?

im running out of ideas here and have been at this for 2 weeks now and nothing i try is working.

tl;dr car is faster without jb4 on any map(1,2,5). same jb4 turns friends car into a beast. wtf?