Drivetrain PROBLEMS, HELP ME!

Hey guys, my problem is this. My car is running really rough lately. Let me describe from the begininning. My car shut down at 105 from the factory, and it was perfectly smooth up to 105. When I got my 3.73 gears a lot went wrong. First of all, from the install however, everything was just fine, (although my car now shut off at 80 since the computer misread the gears throwing my speedo off)... Until I went to Jiffy Lube. They swapped my gear lube and didnt give me the posi limited slip addtive I needed and my rear end was grinding so bad I couldn't drive. I had the car towed to PUR Performance, the place that installed my gears so they could check my ring,pinion, look for any chips or foreign objects. Everything was fine I just needed the additive which they gave me. Total cost: $95. Since my computer was off I got my PCM tuned to correct it all, and especially remove my speed limiter. Now I am at the point where as soon as my car goes over 80,as soon as it passes that certain MPH where my car was previously blocked, it feels like the tranny is gonna fall drop outta the car, and the rear end is gonna blow up. But basically, I think that the tune is affecting my car, and it's showing through the rear end. I checked my drivetrain and everything is fine, U-joints, tranny mounts, everything is good. My tuner said that he didn't set the rev limiter high enough so that is causing the problem, but I'm hesitant. Plus, he won't be back until Feb 20th to try and fix it. Only other thing he's said is If it sounds/feels like someone has pulled a couple splug wires off all at once, it's the rev limiter. So far I've gotten a million opinions from people but it could be so many things because my car is so screwed up. My judgement from the vibrations is also worsened because my power steering pump is broken and it vibrates, my tires have worn unevenly(I can't rotate them), and my body sags 1 1/4'' to the right, the whole car is out of whack. Today I went up to Firestone to have put my car on the lift and check it out and everything was fine in the drivetrain( besides the power steering pump). I had a mechanic ride with me and he was saying how the grinding is in the rear end and that is the problem. I've went to many people and gotten a lot of opinions, and it's hard to pinpoint my problem. I'm tired of paying all this money for things that might work but don't.. I want this solved. I think I'm gonna buy a whole new aluminum driveshaft, get the pump replaced, and get my rev limiter set higher and see how that works out. This is aggrivating because I want so badly to get a stall for my transmission and its in horrible shape. Basically, what I've concluded so far is that my tune has affected my driveshaft and especially around 80+ where it makes the rear end make a grinding noise, it is VERY loud. I apologize for the ranting but I wanted to include all info to get some more good opinions.

From your experience, what do you think is going on with my VIOLENT vibrations at 80+? :dunno: