I was told that by me breaking in my engine on 20% nitro fuel then switching to 33% that I permanently damaged my engine. Anyone know anything about this? It runs decent. It cuts out here and there randomly in higher rpms but I’m guessing that it may be a tuning issue.

The whole mantra that you must use the same fuel from break-in throughout its life is hogwash. As long as you properly tune the engine (cutting out means it’s lean - more nitro needs more fuel feed!), there’s no issue. If you are using Traxxas fuel, get rid of that garbage and get some good fuel. Blue thunder race, Byron’s, Trinity, or whatever fuel has 10-12% oil of a castor and synthetic blend and really, no more than 20% nitro. You will not gain much at all using 30-33% nitro fuel in a stock 3.3.