Your rear end should never shift! Not sure it's alignment, sounds like install wasn't completed. I'd get'er on a rack and make sure everything is tight, sway endlinks and shocks or t-bolts....everything should be solid/tight! Ask to see your alignment printout, should be right on OE specs. Where'd you have the work done, Sears...PepBoys...Firestone or Goodyear?
Gary

Thanks for everything Shane. Appreciate it bro

Had my work done at Faxon Garage, they have a good rep working on our cars. I'll have them look at it when I give them another visit.

Yea no prob, Gary just put out some great info as well.

I have the print out in front of me. Not sure what caster and SAI is..

I just realized that they used the specs for a sedan for my coupe... WTF. The specs shouldn't be the same correct?

No because coupes have staggered wheels

I'm mad now... Guess i'm gonna bring it back tomorrow. Driving with this fish tail is dangerous..

Sedan's wheels are staggered as well.

I did a comparison of sedan vs coupe alignment specs and the rear specs are totally different.

Just make sure that the toe and camber are at 0(zero).