What do you call the guys that complain about non stock cars?

What do you call someone who actually "complains" about something that you paid for? Probably jealous and/or envious, because it's likely they have a piece of **** for a car or maybe none at all, and it just irks them, who knows, maybe they're just a douchebag? Only way I can draw a parallel and relate to someone who complains about what someone else does or doesn't do is when it comes "garages" I didn't have a garage for 20+ years and I used to complain, comment is a better description, about some garages that you'd drive by and you'd see the door open and it packed with ****, no car or workspace at all. A junk storage room, I thought they didn't deserve to have a garage, what a waste! Now that I have one, who gives a **** what others do!! Haha, human nature.