Slow response off the pedal, lengthy engine warm up.

Two and a half years ago my fuel system got contaminated with ethanol and water. I ended up replacing the entire fuel system, including the engine, over the next two years. Little by little, performance was restored. Apparently the ethanol that got loose damage everything it touched, to some degree, but there is still a problem. It's still quite slow off the pedal, and the engine takes forever to warm up. Subaru's are normally very responsive when you hit the gas. I've been driving them for 11 years so I know exactly how tight they are off the gas.

An important factor in that whole catastrophe was the fact that I had to push on the pedal pretty far to get my car going and keep it going. To get it to go cruising speed on the highway, I had to nearly floor it. After I replaced the fuel filter, much better, but not completely better. So that's when I began replacing the fuel system.

Something else interesting is the fact that when I start the car, I will hear swishing or bubbling in the gas tank for a few seconds. Perhaps gas is being returned to the tank after not meeting enough air at the engine.

The seven or so shops I have taken this car to all think the car runs fine. My primary shop - local Subaru dealer - even thought it ran fine back when the fuel was diluted and going super slow. But I'm the one that's driven it for 92k miles. The catastrophe happened at 70k. It is definitely not fine. I bought this car for the speed, and now it’s slower than the car I replaced it for.

SInce replacing the whole fuel system, lately I've been taking shots in the dark with the throttle system. I replaced the throttle body/position sensor. That made the pedal a little more responsive. But the core problem is still there. I also replaced the front oxygen sensor, throttle relay, MAP sensor, and MAF sensor. The car does not have an idle air control valve. Subaru stopped using those in the Impreza in 2004, so they say.

I thought there might have been a vacuum leak, but I had that tested and they detected no problem.

It's like something is inhibiting air flow to the engine, or just plain not opening the throttle enough. Could something have been pushed out of calibration? ECM perhaps? Maybe something just before or just after the throttle body got trashed? Could the air intake boot have a problem that didn't show up on the vacuum test?