comments:
The timing chain tensioner and the chain guides should probably be done if you have no record of them. It's a moderately easy job to do with hand tools and a light competence with wrenches. https://www.motoringalliance.com/articles/timing-system-service-chain-tensioner-guides.110/ The thermostat is a good replacement every 40k miles / 4 years or so (IMHO). I replace the housing every other time. It's a messy job... lots of hoses and bits, but it's not technically difficult to do the replacement if you can remember (or document well) what clips/hoses/screws go where. I can remember being VERY happy that I had some long-nose hose pliers in my toolbox. https://www.amazon.com/dp/B00YQ7S52S?ref_=ppx_hzsearch_conn_dt_b_fed_asin_title_26 I did both of the jobs above when I bought a 60k mile 2005 JCW. The pulley tensioner is relatively easy to swap (again, basic garage tools). They aren't super expensive and odds are you will be in there putting on a new belt anyway... I've never seen anyone re-fit an OEM pulley. Usually aftermarket pulleys come with some sort of attachment system and the OEM ones are friction-fit, if I remember correctly (probably pulley heated and then slipped on the shaft). Maybe you can find an 0% aftermarket pulley? If you can do it within the rules, stiffening the rear sway on an R53 is a HUGE improvement for AutoX... probably the best thing you can do, IMHO, beyond some stickier brake pads.