If you've got a link for "pure NITROMETHANE" on Tower Hobbies, please post it....I can't find it. As for 45.00 being too high for 100% nitro, the last 55gallon drum I bought was $1750.00, and that was about 5 years ago..... $45.00 for a single gallon is most reasonable.

But back to the question at hand, low to no content nitro fuels like higher compression ratios. Most engines like OS and Picco come with multiple head gaskets, shims, to reduce compression, for higher nitro operation. Pull the headon the 3.3 and see if it has multiple shims. If it does, I'd remove all but 1(one) for 0% nitro fuel, and watch your head temps very closely during the initial tune.