Actually 750-800 is "normal" idle RPMs so I wouldn't be to concerned with that as long as it runs smooth. It is odd that it drops to 400 when you shift to reverse. (???) Some stuff to try:
- Reset the computer by disconnecting the battery for few minutes.
- Check the tranny fluid level with the car running and in park. I'm not sure about the gurgling noise and maybe when you step on the gas the tranny is not grabbing. (Just being safe here)
- If you suspect blocked air flow, open the air box an inch or so and see if that makes a difference. (Just for testing, don't drive around much with unfiltered air getting into the engine.)
- Check again for any vacuum leaks or loose hoses around the air intake.
- Double check that all the plug wires are good and are fully seated on the plugs and the coil pack.
- Test and or replace the IAC. This is an electrically operated valve and may be dead.
Did the car always run like this, or just since the dealer worked on the cats and O2 sensors?
