My car has the 150 Caterham kit fitted. Generally, it pulls well. It does have issues from a closed throttle to opening, in that it occasionally coughs bangs and farts until it clears it's throat. I have been in contact with Steve G who says he can remap the car and improve the fuelling across the range. my query, I guess...do I spend that money or spend a little more with Premier ? I don't know if it would work, but I'd love to have the RBTB if they sound as good on the Sigma as they do on a K..