I have recently had a fuel/air control part replaced in my 1998 Mazda Familia. That was done after replacing plugs, etc. The problem it had was it was sacking really hard but going nowhere, once I got past 1st gear it was a bit better. When the part was replaced it was better for about a week. I filled the tank and from then on it started doing the same thing but not as bad. I noticed that as my fuel tank got lower the car started to run better. It is now 1/2 full and only has a little hesitation.
My question is, can a full tank of gas cause these problems?