My ford focus has trouble accelerating and making a popping noise what could be wrong?

My2003 Ford Focus has the same problem (accelerating), but doesn't make a popping noise. I can floor the gas pedal, but it takes several minutes before it registers to 35 mph. I think it has a transmission problem because it "bumps" and jerks like it does, whether taking off from a complete stop or driving down the highway with cruise control set at 70 mph. It doesn't always do it, but it does it enough to be annoying and scary. When taken in to have the meter hooked up, it spits out a code showing that the Solenoid A Switch is bad. That particular part has been changed TWICE now, but it STILL has the same problem. And the engine light REMAINS ON. It's really making me mad! And my car also has headlights that, even on high beam, produce such low light that at night, I can barely see a foot in front of my car. Another defect is the latch on the hatchback (trunk area). Sometimes, it simply will not close! The car gets horrible gas mileage, too. I used to own a 2000 Pontiac TransAm RamAir (5.7L engine) that got better gas mileage than this crappy car!!