I've spent hours searching the net tonight here
Think I've got it, it's a 89 Iboc Pro one level below the Team.
Tange double butted the seat stays are just fork legs welded back there. John Tomac rode Mongoose at the time. Yeti rebranded this frame as there own.
Been riding it around the farm too, handles great can really fling it around aggressively I like it and been wanting a 26 inch bike to use as a proper mtb.