So, I noticed this thread when it began and read a few posts but saw that was being handled and didn't need my input. Then last weekend my 240 began stumbling around 4-4.5K rpm and I revisited the thread to see if the problem might be related. The final solution is contained in the above title but first here's what I did: I checked voltage at the battery and the Pertonix feed wire, I took out the GM 120 amp one-wire and had it checked (no issues). The battery was 7 years old so I replaced it and installed a new fan belt. Checked all the spark plugs, replaced the cap and rotor, and installed new fuel filters (Holley 100 micron before the Mallory 110gh fuel pump and stock fuel filter in the engine bay). Checked the fuel pressure and flow under load. Disconnected the MSD - 6LA box and hooked up the Pertonix directly to the positive side of the new battery. After each of these changes I took the car for a test drive. It got better but not perfect. I could drive it through 5,000 rpm but it stumbled when you pushed it hard. Then last night after the 13 inning RedSox/Phillies game I had a thought. So this morning I removed the covers on the Mukunis and found two of three of them had loose jets. Once tightened the car runs up to well over 100mph and has no hesitation at all. I doubt this will help the original poster as i'm guessing he has stock SUs, but I'd think about looking at my carbs before doing anything else. When you're a Jet.....snap, snap (go ask your parents).