^^ Hey man, it's all good. No rush at all man. It's your setup after all
As for the exhaust, how much money does he owe you?
Is All Star Muffler over there on Hammer close to Copeland Sports and Firestone?
Getting a custom exhaust made isn't necessarily a bad thing. Most muffler shops don't do mandrel bends on their exhaust pipes though. Mandrel bending is where they bend the pipe a special way so that the diameter of the piping stays consistent throughout. If he does some bad bends, it could restrict airflow and possibly even flow a little worse than stock.
If you're thinking about going with just some custom piping and mufflers, it might be okay. In terms of performance, an exhaust doesn't add much to a stock car, so even if the setup wasn't for optimum performance you probably wouldn't be losing much power unless the custom exhaust system was really terrible. Just be careful, I would have them leave a resonator or two. Otherwise it might be too loud.
To be honest, I think it's a little ghetto, but if someone owes you money and if you don't think you can get it back any other way, it might be worth a shot.