98 gems (just written off) 135k used sea foam at 116k no discernible difference but she has/ had regular oil/ filter changes, the odd tank of bp super fuel ( tried shell but didn’t make the difference bp did) and a very clean maf
When I bought mine a year ago I dump 2 cans into the empty tank then filled it. I did this twice. I didn't do anything through the intake. Just cleaned the throttle body. I did flush the oil I believe. But can't quite remember. No issues though. And mine has real good pick up. It's a 00 Bosch 4.6. New wires plugs air filter and snorkel.