A/F is a bit pointless unless he's doing his own tuning or having a in car tune. Plus $100+ yea costly just to have it to fill his pod.
NOtice i didnt say a wideband a/f setup. A narrowband A/F is about the same price as a volt gauge however i dont think glow shift sells them. and another idea is oyu could always use a boost gauge because it will also show vacum which we have you just wont pass 0 lol