aggravated ~ HELP

1993 k2500 454 4x4 . first of all im disabled so I really don't want to spend a lot of money guessing on what may be wrong. 2 excellent backyard mechanics are working with me to solve my problem which is getting worse everyday. what aggravates me is there are several parts that have similar symptoms when bad. my fuel pump was replaced 3 years ago, brake booster 1 year ago, and recently alternator and battery. my current symptoms : sporadic idle - but mostly drops , rough idle , in gear tach will drop under 500 and bounce or truck will just die. if power braked to keep alive its impossible to keep at constant tach range. runs fine while accelerating but randomly at highway speeds will lunge and rev. no backfires, no smoke but service engine lights on. just replaced iac valve cuz it was faulty but it didn't solve problem . from what ive gathered it can be tb gasket , map , o2 , egr , fuel pressure regulator/filter/pump , intake manifold gasket , vacuum leak (found one from can to tb but didn't solve) .

with idle problems I would replace the EGR and all the old vacuum lines also the PCV.