Xj 88 Renix
My heat blows bt it's really not that hot or even warm really
It also doesn't blow real hard
What is wrong?
Any mods to fix it?

Backflush the heater core to get the coolant flowing properly again. Look on youtube, there is a video explaining it, or search for a how-to thread.

If the fan is weak, it could be either the resistor or the blower itself (again, youtube these to figure out which yours probably is).