My '88 2.6 runs normally with the vacuum advance disabled. Be sure you plug the signal line so there is no vacuum leak. The only difference is no part throttle advance from the EZL. This lowers emissions.

So check that you don't have a leak in the line, including that formed rubber hose on the inlet manifold nipple. Mine split on the bottom side, which was tough to see without removing it and spreading it apart. That 3 mm nylon tubing gets brittle with age and can split. I replaced both the above parts. The short rubber hose to the EZL was okay, probably because it sees less heat.

Also try the spare EZL. If it works the installed EZL may be bad. If the same problem it's likely something other than the EZL.

Duke