Hey,
I just bought a OS 18 cv-r to put in my mt2 and need to know what is the max temp i should run and not get any damage

Not do any damage? Well, that's all relative really, but in general once you get over 270ish you're really starting to get into the danger zone. I'd stay between 220 and 250ish. (250 being your max). Some people even go up to 255-260, but I wouldnt.

do you measure your temp at idle or afer a high speed run?

thanks.

I always let it warm up, then do a few high speed runs back and forth then instantly measure it before it has a chance to cool down; Point the temp gun right at the glow plug.

i dont have a temp gun, i have the one thats one the car