Idle problems typically point to vacuum leaks, which means anything connected between the MAF and the cylinder head. That's a lot of ground to cover on these cars. Jfoj has the best thread on this, and I know you've seen it. Have you looked at everything he covers? The fact that your problem comes and goes can help you pinpoint it. Notice the conditions when it happens. Is the car warm or cold? Is the weather warm or cold? Does it only happen at idle? You get the picture. If you can correlate a situation that exists every time you have this problem, you are close to solving the problem.
“The test of the machine is the satisfaction it gives you. There isn't any other test. If the machine produces tranquility it's right. If it disturbs you it's wrong until either the machine or your mind is changed.”
Originally Posted by Mike Miller
I just don't know what I'd do with 560 hp that doesn't involve getting arrested.