ok here the deal my brother is having a problem he has an 05 sti and we just installed his APS front mount intercooler, APS intake, APS bov and while accelerating the car pulls hard but when he daily drives it and he goes to partial throttle the car kinda stutters hard i mean it bucks, if he gives it more gas it stops or if he lets off it stops my evo use to do the same thing when i had the hks bov on now i have the APS valve and no problems i figure its got to be a boost\vaccuum leak or the bov is causing it. he told me to ask here because he has been on here and has seen that people on here know what theyre talkin about

ojh yeah i also told him "see what you get for gettin a sti" he got pissed

 

bump over 12 hrs and no reply wow

 

I would say possible boost leak. Make a boost leak tester and try it. You will be surprised your results

 

i thought if there was a boost leak that the sttter would happen while accelerating

 

its the bov i used to have an sti 04 javablack to be exact.. when put my turboxs fmic on
i had major buck its all the bov its not opening long enough to release pressure what its doing is open close open close open close very quickly which is why its bucking.......
some bov';s have different springs aka pressure controler some use washers with springs what ever kind it is try taking out washers, or put a softer spring in it good luck....

 

^^^^ thats what i had in mind, but i want to get other options(possiblities) before he goes orderin another bov

the APS bov doesnt use differnt springs or washers (i dont think)