Exhaust advice for '93 1.6 Scooby engine trike.
 

I converted my VW based Boom Trike to a Scooby 1.6 three years ago. I made my own 'temporary' exhaust by adapting the standard manifold and, from the flange, welded up a box to distribute the gases either side to separate 18" long MIJ straight through silencers. The O2 sensor plugs into the aforementioned box. The sound is not loud, has little burble but has often been described as 'smooth. I now need to replace with a stainless system but I would like the traditional 'burble' (some trike mates says it's way too quiet!). I know I need an unequal manifold - but what about silencers, size of pipes? BTW, there is no cat. Advice would be very welcome.