trying so hard to fix this problem. Help!

Hey guys im new to this particular forum but im gunna get right down to it. I own a 2002 325ci supercharged by active autowerke. Ive come across a serious problem. my car Boggs really hard from 2800 rpms on (although it varies in some gears) it Boggs out and after i restart the car it stalls out at low rpms. I can barely make it up hills without down shifting to get power at least 3 Times. I automatically assumed vacuum leak, i had that fixed along with replacing the 02 sensors same problems. I got fault code p0340 intake cam position sensor i thought that was surely it, replaced both cam sensors still the problem remains. im exausting all options the only thing i can still think is the MAF any ideas guys PLEASE HELP!!