my car has a high rpm miss in it,breaking up. i checked the plug color after 4 runs and there pure white. could the jetting be causing the breaking up? does it soumd like its lean? Dave

might be missing because its lean, the idle circuit is lean, making the overall mixture lean, the idle mixture screws effect more then just the idle mixture.

Did you check the PV?

From Patrick James "Under the scoop"..

If the proper design is on the car, jetting is simple. You jet up typically 2 numbers at a time until you see the mph or engine performance drop off (depending on the application). Then return back one number. At that point you make another pass/run/lap and begin examining the plugs for corner to corner jetting requirements to balance the engines air to fuel ratios for every cylinder.

I would not rely on porcelian color for jetting. Take a look at Pat Kelly's sig this site for some good plug reading info.

or lack of fuel pressure? mine will break up if I forget to turn on the electric pump, the Carter street/strip pump just can't keep up.