I have a leak coming from the throttle heater so I went to the rover dealer to get the new gasket kit and put it on. About a week after driving with no leaks the check engine light came on and upon start up it seems to have a small misfire and I noticed the throttle heater is still leaking. wth!!!! do the throttle heaters themselves actually go bad or what? BTW I believe this is the root cause for my blown headgasket which was replaced last month and ever since this car has been a HUGE pain in the a$$.

 

First, the heating unit can't throw a code, go to Auto Zone and grt the codes read fr free and get back to us with it.
I doubt the very minor leak that that heater unit can leak, wouldn't have cause the head gaskets to fail unless you never check your fluids.
If the dealer install the new kit, it is covered for 1 year so have them recheck it.