Don't beat yourself up over the XYR/Concept. It's one of the most disappointing cars in the game, it gets about 220hp and it can't get a race mod; thus, all you gain is a big spoiler.
Instead, get a '95 All-Trac for power or an '88 All-trac for a Celica on the cheap. Or win the 200Mi Laguna Seca Enduro...