New exhaust what about the re-map.
 

I'm getting a full Lazer system fitted to my K5 today and heard you guys saying it will need re-mapping for the best results quick question of how much does this cost and where can I get it done the bike is in the Ruislip area. Thnking you for any help. :D

Indeed, the full system will lower back pressure, but is only 1/3 of a solution.

you can generally get away with a slip on and not have to play with anything else, as the headers are retained so it only makes a minimal difference to the back pressure, however a full system with change that and needs to be done in three parts

1. exhaust system
2. air filter ( need more flow to balance out the freeer exhaust).
3. fuelling (remap or rejet if carbs (yes I know you said K5, but this is a generic answer)).

All three need to be balanced to get the best from the bike, any one to far out and you could be running to "lean" (hot) and do damage or at best have dead spots in the throttle responce, a power commander (£200-£300) is one solution or a Yoshi box to tune your ECU ( £70-£100 with dyno run) is another.

who ever is fitting the exhaust should be able to advise you on setup, if not fine you local dyno centre, or contact the exhaust maker?

Cheers Mark.