Hi just got a supersprint manifold for my Cinquecento is it worth getting a decat made and fitted at the same time or should i just leave the cat on and fit the manifold
Having a decat made up is unlikely to give you much of a performance increase, is likely to cause problems at MOT and roadside checks, and will probably cost more than a McCritch chip, a bigger TB or even a second hand GSR.
If going for a TB, then, tricker 40mm job apart, there's a Pug/Citroen one which is 36mm. alanhelen (Martin) has posted a lot of stuff about how to fit them. You'll pick one up for less than £30, just make sure you get the Weber/Marelli one, not the Bosch one (perils of dual sourcing).