So, it's a turbo 4 cyl. Chances are, with a straight-pipe. You should know... Just as every other person here, you need to let your vehicle warm up, before you put it in gear & take off. You also need to take it easy with the accelerator, until the engine is up to temp. At least wait 10 secs. before you take off, then don't romp on it, until your oil is up to operating temperature. That has nothing to do with your situation, I know... Just with some of the comments I've seen, thought it may help save an engine or two. I want to side with you, I can imagine how fucking irritating it is. Now, you said it's probably a rally car with stickers & shit... But he's in an apartment complex... & Drives it every day. A couple people here had good points, saying to use it as motivation to move the hell out of there. I agree. Wait, you said it's a Fiat? Okay, is it a classic Fiat? It doesn't sound like it, based off what you said. It is probably either a Fiat 500, or a Fiat 500 Abarth. Listen, if it is a base model 500, this guy is a faggot who cut off the exhaust, & ...IDK what you could do. Bitch at the apartment tenants? File a noise complaint? If it is a 500 Abarth, it is a turbo 4 Cyl. (which has no muffler) & has a fake crackle/burble sound in the exhaust to sound cool. I could understand your issue, especially if you're not a car person. With a turbo though, yes it needs to warm up, & he's just being responsible. Still, those four bangers are raspy as hell. In this case, there's not much you can do. It's a stock car, & if you complain, it'll just create drama when he finds out who complained. I apologize, I never intended on writing this much. I can just see this from both sides, as a car guy, & someone who's lived at a shit-hole fucking apartment complex, & a duplex. Look at the emblems. If you see little scorpion badges on all four sides, I guess you have to deal with it. If it just said "FIAT", you may be able to get him to put the muffler back on (depending on your state.)