Moki's were not madev to run on nitro. Here less is better. Find a 5% Moki blend and use this. Also check all fuel lines and be sure they are large diameter! also check the tank for this and if you have to, drill out the clunk.
I had this same problem on my 1.8. Completely different engine once this was done.
Also you should have twice the output air volume as input with your cowl otherwise you will get a airlock in side the cowl and cause overheating like you said!