Higher RPM Hesitation

[c3golf]

My 2005 X3 hesitates when the rpm's get higher, like when I'm in passing gear. I've checked the normal stuff like the air filter (removed it and it ran the same). And on a really cold day, had a problem getting it started - it just turned over without catching after it initially felt like it would start. Finally started after pumping the heck out of the gas pedal. Once started, it ran rough for about a few seconds, and then seemed normal. Thought I might have water in the gas, and put a bottle of dry gas in. Didn't help on the hesitation, but since the weather hasn't been as cold, I don't know if that's fixed yet.

Considering replacing the fuel filter assembly, but at over $100 for the part alone because the assembly includes the fuel regulator, would like to have a better feel that this will fix it.

Only 60K on the car and have had all regular maintenance done.

Don't know if the two issues are related. Any thoughts?

Thanks in advance!