heat problem on 3.1l

I have a 1992 chevy lumina car 3.1l with 90k on it.
I have done everything to this car.2 waterpumps,a rad,2 heat core,3 therm,had system flushed and the air out of the system.I still have no heat just enough to defrost (very little)NO leak and oli is fine (no white foam). Mode door works fine no vac leaks under dash

Do you mean that the air is not getting hot, or just not blowing very hard? If it is not getting hot, that usually points to still having trapped air in your cooling system. when you open your bleed screws (both of them) don't just let it bubble, keep the screws open until you get a steady stream of coolant. Also while the screws are open, squeeze your upper radiator hose to make sure there is no more trapped air.

Luminas seem to suffer commonly from the cores getting slimed up with algea and mold and dirt to the point that there is no airflow through them. I'd think that would have been noticed/cured when the heater core was replaced, unless the A/C core is the problem and it wasn't noticed.

Do Manny's suggestion if the temp is the problem. My thought relates to no airflow w/good blower operation.