2000 Volvo S80 Car starts, idles crazy, spudders, stalls. T

I have a 2000 Volvo S80 T6 Twin Turbo with 139,000 miles on the car. However, I just did an engine swap with a factory volvo replacement motor with only 43,000 miles since then I have put 4,000 miles totalling up to nearly 50k. Anyway, ever since I got the car back something new goes wrong weekly. Starter, alternator, fan, intercooler, radiator, emissions, motor mount, etc. Almost everything in the engine bay is brand new.

Anyway, I will get to the point. Yesterday I was following a truck going 25 mph in a 55 mph zone. I had to pass this semi with limited space and even with my 250+ hp I decided to switch from automatic to slap shift. I was running in 2nd gear with the tac at 2k, accelerated and passed, reached 4.5k and attempted to shift up to 3rd. However, something happened and it seemed I lost power so immediately I took the shifter straight to automatic drive. Car drove fine for the next 4 miles, the only thing I noticed was my cruise control light went out and would not come back on. Pulled in the driveway, the car spuddered and died, drifted the rest of the way down the driveway and shut the car off, popped the hood and let it cool down. I did a quick visual inspection of most of the vacuum lines I could see. Disconnected the battery for 20 minutes, then tried to start it again.

Starts up and spits and spudders, idleing and shaking like a dog shitting peach seeds. Car shakes, rpms range from about 1k up to 2k down to damn near 0 but usually lasts about 30 seconds to a minute before it stalls. I tried to prevent it from stalling and keeping it running longer with a little throttle. Immediately stalls as soon as I raise the RPMS. I can start the car up and try to back out of the driveway, I have made it about 10 feet at the most before it stalls and I coast it back down.

I need a hint, I need something, I need to know what to look for, where to look for it at. I want to know what it could be, how sever it could be, and how simple it could be. Any help would be GREATLY appreciated. Thank you.