my buddy has a 1987 dodge ram D-50, has the 2.0 mitsubishi engine and manual trans and mikuni carb. several years ago he bought a brand new carb for it, installed it and drove it for a few years, he let it sit for a few months and now it wont run right. It will start and idle but idles slightly rough and accelerates slowly but when you let out on the clutch it just dies, putting a load on it kills the engine. you can rev it up in neutral fairly good but it just dies when trying to take off. any ideas?

Mikuni carbs were notorius for gum and varish issues as well as mixture control problems with the electric enrichment solenoid

Pull the air cleaner and clean the air bleeds inside the carb air horn.

if that doens't help you need to go inside it and clean it out

already pulled the carb apart and cleaned it out, wasnt that dirty, all diaphrams looked real good..

Major problem with the Mikunis is their plastic float...
They develop small cracks or pinholes, hard to see..
Another issue is the fuel-cutoff solenoid on the bottom
below the bowl, this solenoid is normally ON. But would frequently not be fully open due to mechanical restriction limiting the primary fuel flow.

Years back when I traveled to Japan on business every few months, I would hand carry back new floats for the local carb rebuild shop..

Just my $0.02...