I have a 99 Dakota and my Heater only blows hot upon acceleration, I replaced the Water Pump twice and wonder if any aluminum chips from
the bad Water Pumps might have plugged my Heater Core. Anyone else out
there experiance the same problem? If so any tips on backflushing the Heater Core. Thanks,,,

I would look into replaceing your thermostat, i had a car that did the same thing and that took care of it.

Remove the 2 hoses from the heater core and use a garden hose on both nipples to flush the heater core.

thermostat could be sticking