Bought a BUM X5...WHAT WOULD YOU DO?

[JCN83]

Guys, after two E46's I purchased a 2005 X5 4.4i (V8) with 32,000 miles on it. I bought the car back in November and had no problems for a couple of months.

1 Month Ago: I got my first check engine light. Took the car in, they said there were no problems, gave the car back.

3 Weeks Ago: Check engine light. Car in for service. BMW diagnosis "Engine Misfires". Replaces gas cap. Gave car back.

Last Week: Check engine light. Car back to BMW. Again - Engine Misfires. They test drove...the car "went crazy on them" (never happened to me).

THEY'VE HAD THE CAR FOR A WEEK AND HAVE NO SOLUTIONS YET.

So, I called the Pre-Owned manager and left a message yesterday to tell him that I'm kind of apprehensive. Of course...the only two times we've gotten snow in Cincinnati, the X5 has been in for service. Kind of defeats the purpose!

Should I "raise hell" and demand a replacement? WHAT WOULD YOU DO?

Thanks for the input! I'm on edge...