I'm thinking of building a Sylva R1ot with an R1 engine. Do I need a CAT for SVA? if so, is there a bolt-on CAT that I could use or is it more complicated than that?

Any post 95 engine will require a CAT and Lambda test. If it's an injected R1 you may get away with just a cat (Some have some havent). If carbed you'll need to get hold of an air bleed system as well as a cat. I rented mine from Fisher Sportscars but I think a few other kit manufacturers can supply.

If you want to buy a cat I can recomend powerspeed --- link here --- who can supply. If you buy a complete system from them they used to lend out a suitable cat for SVA.

No connection just a satisfied customer.

Cheers

Jim