Windstar Deep Roarin sound

In the spirit of re-posting, just wanted to let you know, car is much better but still hesistates and now makes a loud noise when at lower revs.

Can I do anything?

Has premium gas in it, and 1 can of Sea Foam and one of Chemtool b-12.

What sort of roar? This could be caused from a variety of sources: wheel bearing, exhaust issues, wheel alignment, etc. Can you compare it to something familiar?