Intermittent Heat - only when REACHING OP. Temp.
 

So the weather is getting a little cold here in Canada...

I've done some snooping with the search function and google, and I'm thinking I have some air in the cooling system.

However the sources say at high rpm's, if its air in the system, you should get heat back.

Well it blows nice and toasty as it gets close to operating temps. then right after I'd say it reaches, it gets cool.

This is both in the city and on the highway cruising at 3k. I tried downshifting to bring the rpm's into the 4k range to see if it will pass the gas and give me hot air, but it was still cool.

Is this still a sign that I have to vent the system or could it be something else?

I've been having issues with my cooling system, and I recently replaced my heater control valve and I wasn't getting proper heat. Turns out i had it installed backwards... I dont think that's the case with you, but that plastic heater control valve is worth looking into. Maybe it's old and stuck...