I'm guessing that you speak from experience on the nitrous?

My dad replaced the head gasket with a sheet of notebook paper on one when he was a teenager. He said it had so much compression that you had to put both feet on the deck and pull... then it would turn hard at that. He ran it on a mixture of gas and model airplane fuel (had nitromethane in it)! He said that little 3 horse briggs would mow through anything. That is, until the notebook paper headgasket finally gave out. I guess that my granddad asked him why it didn't have any power, after he put it back stock (gramps had no idea what had been done to start with ).

 

My God! Buy her a new mower! You guys need more to do! LMAO!