So first off, i've been having some issue with the tailights on my 99 f150. the tailights will not light up at all as normal runing lights. but, if i hit the brakes they will light up. As well, the turn signals work and the hazards work. i assumed it would be a group but i looked under the kick panel and the grounds were fine, and underneath the truck bed there is a ground on the frame that looks slightly rusty. Could it just be a cleanup there? Any insights here?

Secondly, it seems as though i have major performance lack. Even in 4th gear the truck seems to be straining itself to pass another vehicle at 70 on the interstate. I have seen advice saying to just clean the throttle body and that should help (and improve MPG). Would that be a sufficient improvement, or would it be worth to get a CAI or even a new bigger throttle body?

Thanks in advance.