Any chip from a reputable seller should come with some warranty, maybe try one of those you listed and see if theres a money back guarantee on them ?
We used to do M42 chips on the site but the applications were so varied it was a non starter in the end, got some good results though so dont dismiss a chip change.
work out the BHP gain per Ԛ£Ã”šÃ‚£ and they can look quite cheap
as always pinch of salt with all claims but you should be ab;e to tell the differance with your arse dyno
HTH
