It's hard to put a finger on what all the issues might be, so I can't say positively that noise is one of them but it's highly likely. I unwrapped the right bank upper harness and tapped the 14ga pink wire for power Sunday. In the process I created a small rat's nest of wire that could be contributing also.

It doesn't help that I'm only getting about 90 minutes a day to work on it, and those are usually distracted minutes. Words cannot describe how anxious I am to get this nailed down and move on to yanking the engine and fixing the oil leak, etc. I'm sure that impatience isn't helping.

I managed to get an order placed yesterday with digikey for some rc filter parts, a spare boarduino kit and a couple proto boards. Hopefully I'll have that this weekend and can try cleaning up my wiring mess. Between chasing noise / count errors and soforth I've been contemplating how to package the thing for underhood conditions - would love to hear ideas here. Mine is going to be dead simple - potting the whole thing in epoxy. Possibly an external m+f weatherpack connector set for the power, uart and inputs (10 pins total if memory serves) and then either 10 or 16 loose-ended pigtails (8 ttl pins and either two or eight ttl grounds) for the coil igniters coming right out of the epoxy.

Work's been busy lately so I haven't had much time to research and audit code. Today I was hoping to look for a wiring diagram because the info at http://chevythunder.com/lt1_electrical_page.htm isn't close to what my Y body has - there is no tach wire on my black coil connector.