If you had to keep one cat on a classic, either downpipe or centre, which would you choose? It seems logical to me that you get better turbo spool up with the downpipe cat removed, but someone said that the Japs reckon you get better power with the centre cat removed.

Do you have to declare a decat pipe on your insurance?

 

AFAIK -but check with the experts- the most restrictive CAT in terms of both power reduction and delay in turbo spool up is the one in the DP. If you just retain the centre one, the car should still pass an MOT ok, but you may need to get it very hot first due to its location.

Yes, ALL mods must be declared to the insurance company, policy validity is contingent upon absolute disclosure.

Regards,

NS04