Combustion chamber/valve deposits and sticky injectors are certainly likely culprits.

Other possibilities include a bad knock sensor, bad ECU, engine overheating due to a degraded cooling system, clogged fuel filter, dying fuel pump, bad o2 sensor, wrong heat range spark plugs and an inoperative EGR system.

I'd start with some fuel additive to try to clean the injectors.... might help, might not.

Frank

'89 [color:"white"]G-Raider[color:"white"] [color:"black"]Supercharged 3.0L, MegaSquirt 2, lockup A/T, 2.5" exhaust, 172k, Cibie H4s/Oscar SCs, Hella Micro DE fogs, Cobra CB, Superwinch hubs, LSD rear/Aussie Locker front, Bilsteins, Lifeline AGM, Rust-Oleum