I notice that when I am going uphill, that's when the struggling starts, I have to wait, keep the pedal on and wait until it "clears." Another thing is that this happens under load, when I have the car on idle, parked and I depressed the gas pedal, it runs fine, in other occasions it sputters a bit but generally runs smooth. However, when I actually drive it and I have to go uphill, bam! It won't go smoothly, stalls, boggs and only after a while it clears.
Sounds silly but try BACKING up that hill and notice if anything changes.