Car Issues

[gettysburgfreak]

So on June 4th I purchased a 2005 Cadillac CTS from a dealer in upstate NY. In that time I have gone back numerous times to have an air bag sensor replaced and to fix my steering wheel that has shimmed. They said they replaced the tie rod and front drivers side rim that was bent. The shimming has mostly went away but still vibrates once in awhile. Fast forward to a few days ago..

I am driving down to gettysburg on Monday with a friend of mine and while on US 15 my car starts to hesitate. Nothing major at first but enough for me to take notice. While driving to Baltimore on tuesday it gets a little worse, yesterday driving to DC gets a little more hesitant. By today it was hesitating very very badly, so much so I cut my trip short to come home today. It also makes a fairly odd clunky noise and sounds like a diesel engine. I called the dealer and they are going to look at it tomorrow.

My question is this:

What do you guys think could be a possible issue
What are my rights in terms of the lemon law?