Personally, I'd fit one of these first:
https://www.dmgrs.co.uk/products/gen...5480-stc000110
It's the original factory-fitted part that usually lasts 10+ years, and some are still in service today.
Plus they're very cost-effective as a way of diagnosing other issues - you'll likely find everything is OK once this is fitted.
It's certainly where I'd start.
