I have been having a similar problem with my 1994 850T (112,000 miles). Sometimes it sputters, pops and then starts running normal. Also it will not take full throttle well. It seems to lose power with too much throttle imput, but when you let off it resumes normal excelleration. After changing the front O2 sensor it seemed to improve the putt putting. My codes showed misfires in each cylinder. I'm beginning to think that the catalytic converter is partially plugged. I will have to have the cat. checked out further. I'll update if anything comes of it.