Here's what I've been able to find:
Other TaG Karts
This is the Exciter by Mayko. The machine is designed specifically for adult karting enthusiasts. It has 3" wider frame rail spacing and 1 1/2" longer wheelbase to accommodate full-size drivers. It is powered by a Yamaha 225cc SOHC air cooled, electric start 4-stroke that makes roughly 25hp, has a 6-speed gearbox, and includes front brakes. At a package price of under $6,200, this is an interesting machine. Maintenance is essentially nill, with 300+ hours to major rebuilding. Unlike 99% of the kart engines on the market today, the Yamaha motor pulls like a draft horse off corners. The chassis is well matched to the motor, and feels stable and smooth. Unlike the zingy little 2-strokes, this monster produces a serious, but manageable wallop that is fun to drive. Downside: No real class to run it in - yet. Single cylinder engines are also pretty thumpy, and the chassis is not well suited for other class applications.
TURBOKART
It appears to be a TaG Spec class that never took off....just wondering if anyone here has seen these.