Im almost at the point of getting a honda!
I had a similar problem in a pickup, it was exactly as you described it. Take your gas cap off and drive around to see if the problem re-occurs, if it does not, then you have a clogged vent tube, when the cap is on and engine running it is causing a vaccum in the tank that builds up and fights the fuel pums for the gas. The best think about this fix is that its free if it is your problem. Possibility two, the pickup in the tank is clogged with junk.
Check out what the tank in my 68 looked like.
What it is supposed to look like:
Here is where the vent tube is:
I had a similar problem in a pickup, it was exactly as you described it. Take your gas cap off and drive around to see if the problem re-occurs, if it does not, then you have a clogged vent tube, when the cap is on and engine running it is causing a vaccum in the tank that builds up and fights the fuel pums for the gas. The best think about this fix is that its free if it is your problem. Possibility two, the pickup in the tank is clogged with junk.
Check out what the tank in my 68 looked like.
What it is supposed to look like:
Here is where the vent tube is: