Air filter bogging low rpms
Recently bought a 2005 Subaru Impreza wrx sedan, mostly stock, other then FMIC, hks bov, oil catch can, 3inch turbo back, MBC set to 10psi, and short ram intake.
Recently purchased a brand new oem denso MAF thinking it was the issue.
Too the problem, the car idles perfect with any brand air filter on i have tried k&n AEM and spectre, all new, but when i go to take off the car bogs and jumps from 1k-3k rpms then smooths out completely, now when i take the air filter off and run an open pipe the idle jumps from 500 - 2k and sometimes evens shuts off, but the car goes through all rpms smooth as can be.. i have been running with the filter on just to be safe and its really not all that bad too deal with but i would like to know why its doing this..
Also, i don't think this issue has to do with the air filter issue considering it does it with and without one on, when i go to shift and let of throttle and push in clutch the rpms go up another 1k and kinda just wanna stay up there but then drop down.. its worse when getting on it, was told its a vacuum leak but i cannot find any.. motor doesn't seem too be too messed with either.
All answers are appreciated!!! thanks!!!!