Depending on the length of the "full throttle passes", the problem could have been your own. These engines are designed to accelerate, and then decelerate, as in what happens around a race track. They are not designed to be run wide open for any length of time. If you were only doing this for the span of 100 feet or so, probably not a problem. But if you were running it wide open until it was almost out of sight, and then back 3 times in a row, then its likely your driving grenaded it.

Your tuning plays a factor here too. While your temperatures do sound in range, it is possible that you may have had your needles out of balance. By having your low speed needle too rich, it can hide the fact that your high speed needle was too lean. This will show up by having your car start off at low temperatures and then climb much higher the longer you run it. Once you get the car and chassis warmed up, your engine's temperature should stay pretty constant until the tank runs dry. If it is going up 30+ degrees, you may need to look at your tuning.

I am not saying one way or another whether you are at fault or they are. Its impossible to tell without seeing how you ran, and without being there when the engine plopped off the assembly line. If OFNA doesn't honor it though, you may want to contact Hong Nor, which is the company that actually manufactures the cars that OFNA sells (OFNA doesn't make anything).