Which exhaust with 133 polini

hi,
what exhaust is best to run with a polini 133 and 24m dellorto with polini reed block?

any ideas…im thinkin either a simonini down and under or a zirri exhaust.[?[]

Both of these pipes havin been hung up in the shed as the header pipes and resonance chambers are too big, hence loosin back pressure. The simonini D & F doesn’t fit too good either and needs moifying rather than just simply boltin on,. The zirri is an excellent fit but needs a zirri short 4th gear ratio.

Last year I tried the zirri on a standard primmy motor and squeezed 50mph barely out of it, switched to an et3 banana pipe and instantly got 60mph.