[4SPEED]

03 GT
started out having P0304 codes and a miss at idle but could never feel it while driving. Intensity of miss would vary, engine temp and outside temp were not consistant. I started checking everyone's stories here and decided it might just be a vaccum leak at the #4 cylinder like others have had. So I dismantled it and found that none of the intake bolts were loose at all so I snugged them a bit more. I doubt that I had a blown gasket. Installed new plugs and wires (Bosch Premium).

Now before going any further let me tell of my credentials so I can't be blamed for putting something back together wrong. Was a service manager for 15 years so I know my way around a car, have a well stocked tool chest and know how to use them all and as a hobby I restore old motorcycles, so I am very knowledgeable and mechanically inclined.

Now for the new problem, the miss is still there. Now the engine does not slow down when letting off on the gas. I have checked it out by putting it in neutral and coasting and the tach reads anywhere from 1500 to 2500 rpms and at times it will start out at 1500 and gradually increase to 2500. The rpms drop once the car reaches 3 mph but the idle is still close to 1000rpm, not the 750 like normal. We have a 1/2 long street that has 5 speed bumps.
I generally drive at 30 to 35 in 3rd gear and let off the gas as I approach a bump so the car will slow to 25 so I can go over the bump. Now the car in 2nd gear will maintain 27 mph with my foot off the gas...almost like it is in cruise.

Sounds like a vaccum leak to me but I can't hear anything with the old stethascope trick of a tube to your ear and I have sprayed everything with the motor running to see if the fluid would temporairly block the passage way.
Oh, no more P0304 codes either.

I'm about to pull my hair out