So I was doing a little street tuning today and noticed something. While doing a street pull, there is no sign of smoke. Even after the pull when i'm rolling to a stop, no smoke. BUT, after I make a complete stop, wait a couple seconds, then start moving again, I get a little white smoke coming out of the exhaust. Some of the times it didnt do it, but most of the time it did.

Could this pose a threat...(I dont really like have the return line curves forward and then back to get around the downpipe. The return line does not flow upward at all).

Your return line is terrible. Thats what your problem is. Fix the return and make it a much straighter down hill shot and you'll fix your problem.

would it be a bad idea to put a 90* fitting in the return line?

hell yeah. a 90* bend is a horrible idea. with your return line being so close to your downpipe, you can get away with running it a little straighter and wrap your downpipe and insulate your return line with this.

A 45* bend is not a bad idea though.