Well,i dont think between 40 and 41mm there will be a big difference,but stock 1.6 and 41mm made around 50% in air flow (with the port only slightly modified at the valve guide).

What are your hp goals? 

now i have 40mm inlet and 34mm outlet valves - its a g60 with boost, so i was thinking about only getting bigger exhaust valves, 36 or 38.. in combi with the 41 inlet, it gets very tight between the valves - do u think it makes a big difference (performance) between 40 and 41 inlet valves??

thanks for the link jeri! hp is looking good, i hope they speak english or a bit german.. whats about szuromiracing, Kacsó-Gép or frenky-tuning?