Standard Exhaust clamp

[Miniac]

I've had similar problems in the past and have fitted and refitted that exact same clamp countless times, my overall opinion is to just do away with the stock system and replace it with a branch manifold, if you're looking to save money you can generally find a decent second hand setup going from time to time, the stock GTS crows foot is a good upgrade over the cast manifold and most second hand mini Spares places should have one or something similar lying around.