Re: mph issue
The surging problems are from fuel starvation. If your engine is too rich and you go WOT and it starts surging, there is not enough fuel flow, AND it's too rich.
Fix the fuel flow issue before you start "modding" your engine.
A new air filter, or putting holes in the existing one will only allow more air in, it's not going to "fix" anything, except a slightly rich mixture.