Troush

All, I have an '04 545i, 6 speed with 88,000 miles on it. Last week driving home (when it was about 19 degrees) the car started shuttering and the catalytic converter light came on and it went in to limp home mode. The car drove like a dog, I stopped the car and restarted it and everything was fine. Yesterday, I started noticing that it is doing a similar shutter when I take off in first gear and if I leave it in third instead of downshift (even thought the RPMS are high enough).

Is this the fuel pump? I was hoping it was bad gas but the fact it continues to do it tells me that it is perhaps the fuel pressure?

THOUGHTS?

Thanks in advance!
Tobey