Jason .. The throttle body was definitely the problem. The difference is that the stock unit utilized roller bearings and the Mustang TB used ball bearings. I changed out the injection system partly because of the throttle body and partly because it appeared that the engine was running lean at full throttle. The injection has taken a lot more time and effort than I thought it would. The most difficult was building a fuel rail that did not leak. The most time consuming is programming the fuel map (still in progress). If I were doing it over, I would have spent more time either modifying the stock throttle body to ball bearings or finding a shorter aftermarket TB. I would have evaluated the stock injection system with a functioning TB before jumping into a total replacement. As it is, I am VERY happy with the results even though I still have a few "driveability" tweaks to make.
190SL, 230SL 5-speed, 95 E320 Wagon, 01 E320 Wagon, MGB, Boxster 'S', 190SL "Barn Find"