A lot of the Georgia Tech Boys and top high school player's went to George Kehlnhofer during the time when Howell was growing up, and yes I have heard that Howell went to him as well. Other Kehlnhofer students included Stewart Cink, David Duval, and Ted Fort. George had a program called Accelerized Golf that was based on TGM principles while teaching a swinging pattern from what I have been told.
George is now teaching at Bridgemill Golf Club with another TGM instructor Tom Ness. I have never been to George or met him, but you do hear a lot about him (he's respected) in the Georgia Section where I teach.
Sorting Through the Circuit Player's Handbook.
B-Ray