Not happy about razor return

I entered the last race with 766 PR. I did spent 210 gold but that was my mistake; the last race was unlocked long before I spent gold. 6 purple parts were more than enough for last race. You get pistons and drive shaft in the last chapter which allows you to max out the engine and gearbox purple parts. I guess you spent cash/parts trying to upgrade blue parts which turns out to be useless.