rough running ram50 1989 2.6 carb

[FMS88]

A bad secondary throttle vacuum chamber won't affect idle or performance at lower RPMs and loads. Its failure causes power loss under load at higher (~3000+) RPMs. It's easily tested. Just apply a vacuum to its port. If it won't hold the vacuum, replace it, which can be done without removing the carb. Rebuilding the 2nd Gen Mikuni can be a challenge and some rebuild parts are no longer readily available. So if it's running fine and mileage is good, don't mess with it. If it starts to go south and it's not due to an external component like the secondary chamber, then consider installing a Weber.

If you want information on the Mikuni's functions and steps to perform diagnostic tests, look at the Chrysler Training book contained within this thread:
http://www.mightyram50.net/vbulletin...3354#post73354
The book is for 87-88 models, but the 89 should be very similar if not identical.