Hello Slanters!I recently bought a 87 D-150 shortbed with of course a Slant6.It runs fairly well but has a,for the lack of a better word,skip while driving at 50 or any other steady speed.I did some adjusting and have a question about timing.The ESA is still in the fender and is hooked to full manifold vac.When I put a timing light on it I can set it at 16 degrees base as per the hood sticker but if I rev it I get no advance.Does it only advance under load or is the computer not operating?

Sounds like the ESA has had it and it's time to consider alternate ignition systems. (HEI is easiest option for a lean burn vehicle, and probably also the best.)

ESA, if working, advances timing with vacuum applied--period.