2003 f150 5.4 /7700 series. motor has 167k and pinging is getting louder. usually under load. it is worse when on highway and i let off gas then resume. i have always ran 87 octane but have tried running 93 and also octane booster. neither hepled. i also ran some seafoam thru the powerbrake vaccuum line. still the same pinging. a friend said possible timing is off? any advice is appeciated.

 

Try removing your catalytic convertor. It's quite possible, some time in the past your truck may have developed a condition and caused your convertor to possibly plug up a bit.
You could also try a thicker oil viscosity and use a 100% Synthetic