I am about to make my exhaust. 1600 with SR20. I have all the parts but I have a question about the flexible exhaust piece. What length should be used? I have a 8" one here, but there is very little flex in it. In my mind it needs to be much longer and hence more flex. So how long should the flexible exhaust part be?

Cheers

8 inch should be heaps

1600's dont have very long exhausts and they didnt come with flexi joins from factory.
For NA i wouldnt worry about one but if for turbo exhaust they are handy to reduce strain on the often red hot turbo and exhuast manifold flanges.
I think even a short one would be more than adequate.
Just make sure the piping and muffler have proper support...