poor hot water pressure
#1

The hot water pressure throughout the house is very low. The faucet has to be turned all the way on hot before warm water will flow out (it now trickles). The cold is fine. The water heater is gas and it has been flushed out.
#2

Since cold water is fine and hot water isn't, the problem has to be either the cold water supply to the water heater, or the hot water supply coming out of it. Lookmat the nipples on the top of the water heater, the supply lines connected to those nipples, and the gate valve on the cold side going into the water heater. Those spots are probably where you will find the problem.