Egr

Go get on www.rockauto.com and drill down as follows:

Dodge --> 1989 --> D100 pickup --> 3.9L (239CID) V6 TBI --> Emissions -->EGR valve. You will find three listings. Ignore the last one. The first one is an excellent price ($26 and change) on a good brand (Kem) on warehouse clearance. The second one is a good price ($37 and change) on a good brand (Airtex). This is a later-type EGR valve with backpressure transducer; it'll reduce the hesitation/stall tendency described by Murray.

Also, between vehicle inspections, run a vacuum hose directly from the carburetor's ported vacuum nipple to the distributor's vacuum advance, not stopping at the OSAC valve on the firewall. Result will be _much_ better driveability and fuel economy.