I have recently had some top end power problems with my 98 XR600. Whilst removing the carburettor to check main/pit/clean etc, I have noticed that the inlet manifold has had the restriction taken out (which is good). On closer inspection I have noticed that the inlet manifold has in fact been filed out internaly... so much so in one spot there is only a wafer thin gap between the sealing o-ring and the plastic/bakerlite inlet manifold. This filed out manifold means that there is a 3-4mm overlap when the manifold is bolted to the engine. I think that this may create turbulance in the manifold at higher revs, thus creating my top end power problem What do you think.