those stacks have a flat outer bellmouth which isn't good but the more important part which is the entrance curve is good and the flange transition is ideal. Looks like the best I have seen out of Japan so far. Good thing it's not like the rest of the stuff that I have seen them make then!

Have you had any thoughts about what I said about the throttles? Bigports have airspeed issues as is, hence TVIS so by having too large a throttles won't help. But I woudl understand you not wanting to change because of what you have already.

Change one cam at a time one degree and see what it does for you, if it's good then keep going.

Now what about filtration, do you run anything?