yes, question for you? 3.1V6? or 3.4 DOHC V6? The 3.1's all come with timing chains I believe, and the 3.4's came with belts. It doesnt matter, but you said euro, so I was kinda wondering if that 3.1 was a typo. Ok, next, Dont rule out the spark plugs and wires. Actually, as I was reading your problem, I immediatly thought the plug wires may be arching over to something when they get warm. Do yourself a favor and if the plugs and wires look bad, chances are they are, and spend a little time and money and replace them. It may solve your problem. If nothing else, give you better gas milage and rule out plugs and wires as the problem. AS for a fuel pump. They are usually either completly good and working, or completly bad, not many cases of in between. You can hook it up to a fuel pressure guage and see if there is enogh pressure there. I think around 40psi is the spec. Not sure. Could also be a sticky injector, have you tried fuel injector cleaner lately? Get some that wont harm an o2 sensor, I was using some one time, and my o2 sensor took a crap. Good luck.