The reason that I ask is because I was sure that the timing was only vac/mech. Trouble shooting will be easier if I have the right info.

I've had some ignition problems and opted to buy an MSD blaster ignition to replace the stock amplifier. The truck runs but I get nasty pinging/hesitation upon accelleration and high idle. It also does not want to go past 3k RPM. It might just be that the ECM isnt getting the right signal and is in a limp home mode. I will call MSD on monday.

I have not yet disconnected the vac advance. I know that sometimes with comp controlled ignitions, the vac and mech advance can be locked out when adding an external module.