I've used these guys for parts for my 2005 VW Jetta TDI since 2006. Very easy to talk to if you have questions, helpful & knowledgeable, they check out their parts (no Asian junk here!), ship quickly, and their prices are competitive. (Pretty sure the founder is still driving his A4 TDI, with around 300K on it...) Have started using them for our Sprinter as well. Not surprised they have a concise publication like the one on the link above; very good info!
Disclaimer: I have no affiliation with idParts, other than as a satisfied customer.
Agree^^^^^^^^^. It’s so common many gas vehicles have a light on the dash “tighten fuel cap“ as the first warning. Second never heard of LIMP because of the fuel cap. It’s very minor as far a emissions in the BIG picture.