Well, I feel like I want to clarify some things about glow fuel before i suggest a solution to the nitro-problem.

Glow fuel i based on methanol with an addition of about 20 percent oil and usually an addition of 5-30 percent nitromethane.

In defense of spaceman spiff I must say that Nitrus-oxide and nitromethane may be two different things, but they do exactly the same thing, they add oxygen to the combustion chamber thus creating a bigger explosion which give more power to the engine.

This is why you need to have a richer mixture when you use more nitro otherwise the engine will run lean. Think of nitro almost like having air in the fuel...

The downside with nitromethane is the impact on the environment, thats probably why nitromatheane is more expensive in Europe, we probably have some sort of tax on it.
When nitromethane is combusted something called NOX gasses are part of the resulting products, these are poisonous and harm the environment.

OK, how do i get more power without using nitrometane? For example there are European and Russian made engines which are made to be used without nitro or with very little (5%) nitro in the fuel, and they still produce the same power. What's special about these engines?

Well, as I mentioned earlier, nitro adds oxygen to the combustion chamber which creates a bigger explosion. Another way to accomplish the same is to increase the compression in the combustion chamber.
This can be achieved on an engine that needs more nitro (IE OS) by using a thinner cylinder head gasket or by simply removing it. The next thing you need to do is remove the cylinder lining and increase (heighten) the exhaust port with about 1,5 mm on a 46-50 engine and about 2 mm on an 60 engine. These two modifications together is equivalent to about 20 percent nitro in the fuel.

There is one possible negative effect when you do this modification, if you increase the exhaust port to much it will have a negative effect on the idling characteristics, whereas addition of nitro in the fuel actually also improves the idling of the engine.

Observe that I take no responsibility if you do this modification on your engine, do it on your own risk, but if it is done properly it works.

/Mattias