hi, I just noticed that there is a mismatch between the header and engine on my new 160 gas engine. the exhaust port on the engine is basically larger than the entrance in the tuned pipe header. I suspect this will not give the best gas flow so I wonder if dremelling away a little metal on the intake of the header(chamfering the edges all around) would give measurable improvements on rpm and power. As things is now I see rom for improvement or is there any sensible cause for this mismatch??

I can't believe no one would answer this.... as a general principle, when using ANY exhaust system, I make every effort to match the ports. IF nothing else, it smoothes gas flow. In the old "tuned pipe 60" days, we actually "flowed" headers, meaning we carefully shaped the port and the curve of the inlet port to match and optimize flow. We found a considerable rpm tuning difference between the "flowed" headers and the stock mis-matched, irregular interior ones.

Ain't scientific, but I believe it is a worthy effort to match them.