Swap running a little rough Options

[gtfc115]

So i got a lot of little maintainance done on my swap. i still need to replace the plugs and wires and probably distributor. ive had problems with my IC piping blowing apart, but they are about as tight as i can get them now. i also need to get the exhaust re-done...i have a huge leak where the DP meets the rest of the exhaust, and its only 3" half way back.

anyway, while driving, boost builds fine (still only @ 7psi) but if i go much further than 4k rpm, it seems like the power just drops off and the car starts studdering/hesitating. this problem is worse if the engine isnt warmed up yet. i have a feeling that a new exhaust will help a lot with this.

also, if im at full boost for more than a few seconds, and let off the gas and put it in neutral to coast, the rpms will totally drop to 0 and the engine will die.

this morning, i was cruising around, and came to a stop light. the idle got really rough, jumping between 200-700 rpm, then it died. it started back up just fine and was perfect after that, but still had the symptoms above. when i got home and shut off the car, i could hear a very slight hisssssss coming from around the throttle body. do i have a vac. leak? i looked around, but didnt see anything that was loose.

thanks in advance guys...ive been reading a LOT on this forum, mr2oc and alltrac.net. learning a lot about my new engine. at first i was thinking about selling it, but now i want to keep it and fix it up myself.