Re: any more suggestions for back/chest acne?

Unfortunately there is still not a consensus on the cause of acne. However, your post reminds me of another who has the same problem, EXCEPT when he leaves home (and stops his usual workouts 4-5 days a week).

Since working out causes oil, sweat and testosterone production, I'd experiement by skipping the work-outs for a week or two and see if there is any improvement. If there is an improvement, you'll know what is causing it. If not, it's one thing you can cross off the list.