[Cd]

Hey guys, I took my car into the shop since my car seemed to be acting funny.
The car has no power and dropped in mileage by over 21 MPG within the last few months.
The car has had a basic tune up - wires, plugs, new oil, etc, yet nothing has changed. The guys at the shop managed to ' accidentally' break my coil and the car would not start. I had to buy a new one at four times the cost and pay them over a hundred dollars for the labor ( or get the car towed home ).
They said that the drop in mileage was due to a worn coil, but now that I have a new coil, the car still has times when it just turns over without starting, and there is no change in mileage.
I took the car in because I feared that something else was wrong with the car, and wanted a complete diagnostic check. My check engine light came on every now and then, my speedometer worked, but at other times will not, and the car suddenly decided to not start one day- it turns over but won't start.
They couldn't get the check engine light to come on so i didn't get the code.
I had them run a compression check and they said the car is normal, but I just wanted a second opinion on what to do next.
The transmission is supposedly fine, because it is not slipping ( its an auto ), but the car is extremely slow and revs really high and just creeps along at 45 when it should be doing 65.

Just wondering what you guys would advise me to check for next.