from experience, the little bit more for your tuner to supply and fit is worth it, if anything goes wrong it's up to them to fix it. i had a clutch fitted at the beginning of the year, the flywheel was badly machined and caused vibration at low revs. due to the workshop supplying all the parts and they wernt sure of the problem until it was stripped, i ended up with a new clutch and billet flywheel fitted at no cost except for original clutch only fit.