I have just uncorked mine a little and it seams to of helped her a lot !!!
I took the spark arrester out and took the baffle out of the air box,, I know this may make it run a little lean so Im running a 50/50 fuel mix of AV gas and 95 pump gas,, this raises the octane to 100,,, the AV fuel also gives the slight affect of running rich which counters the extra air flow !!! ... Its basic but works well,,,mine pulls harder of the bottom now and revs out much more freely and it cost me 0 dollars so I recon its worth doing cause she was a bit flat out of the show room...
And hello from New zealand