1989 Toyota pickup 3.0 V6 engine

[rkitchens]

running very rough

[redneckcustoms13]

They all do. Scrap it and do a 3.4 swap lol. 

[Snowtoy]

running very rough

At start up, early running, after running a while?

Have you checked the ecu for codes?

When was the last tune-up?  Unlike the 22r(e), the 3.0 isn't an engine that you can ignore regular maintenance on.

If it hasn't had a tune-up in a while, start with that, if t has, inspect the plugs, plug wires, intake plumbing for cracks, throttle  body for gunk, exposed wires, corroded grounds, etc.

If known, when were the valves last adjusted? The 3.0 is prone to burning #3 and #6 exhaust valves.