EXTREMELY WERID PROBLEM, car shuts off at high RPM's in 3rd-4th gear

My car had been sitting out there for 45 days or so because my clutch died on me, along with oil seals, antifreeze leak. So i just got my car back 2 days ago finally having a mechanic fix all these problems, with a new oem clutch, oil seals, antifreeze coolant line. So on my first day i noticed a little grind after putting it in 1st gear, i think because it needs to be bleed a little bit more, but if i go from 2nd to 1st it wont grind. Or it might need a new slave cylinder. Well anyway thats not the big issue. I have tested my car to see if everything is fine (boost, rpms', etc) by getting on it a little bit (not crazy redlining) and i have noticed everytime i am at high rpms in late 3rd gear, my car would shut off on me. But then i would start it right back up. This has happened three times to me out of 4. Well today was my 4th time i tried it again, and this time car didnt shut off, instead moments later my rpm's were really weird and they would barely go up, it almost seemed like i wasnt getting enough boost in any gears. I know in 5th gear i am getting almost no boost at all after i just tried it right now. The car seemed like it wanted to stall. I dont know what the hell the problem is. Could it be because my fuel injection needs to be cleaned or a new fuel filter? Or my car need a tuneup since it had been sitting for over a month? Could i have a boost leak? Anyone know what the problem might be?

have u checked ur battery or alternator, somtimes before the alternator goes it sends wierd amp's to the battery and the ecu might not be getting right power, therefore would shut down

have u checked ur battery or alternator, somtimes before the alternator goes it sends wierd amp's to the battery and the ecu might not be getting right power, therefore would shut down

You have a good point, but would that be a cause for losing power in the RPMS? I mean it seems as if i am getting no boost at all anymore, i can still hear the turbo spool but the RPM's wont climb over 3K RPM, in 5th, the car wont spool at all. Also, it seems as if i dont rev the car high enough, the car just wants to stall. I dont know what the hell is going on, but thanks so much for your help. Could there be anything else that could be the issue?? I will have the car checked out tommorow morning but untill than i would like to hear about many of the significant things that could make the car have these symptoms.

I had a similar problem that was weird as fck...ended up figuring out that my MBC was installed totally wrong...

Your problem sounds fuel related to me though. Do you have a boost gauge to see what your running? Maybe you dont hit boost because your fuel cuts of before the turbo can spool... plugs and plug wires are the first things you should to though...