Need Heater Help

I need help. I am taking a snowboard trip with my 98 Dakota and I currently have no heat. A few months ago I changed out the thermostat and put in a 180 degree one, and just recently flushed out the heater core. I can get a very very mild amount of heat coming out if im on the highway "gunning it", but other than that I a freezing. Any ideas or suggestions would be greatly appreciated!

Could it be that I need a new heater core? I thought they would only need replacement if they were leaking.?

Thanks again.

sounds like you have no or little coolant getting to the heater core.
On a 98, it is most likely not filled with crud, which could cause that, so I'd look at the bypass If I were you.
next logical step is to check the climate controlls and see if they are working.