ORIGINAL: pe reivers

engine dying at mid-throttle is a carb problem. Many carbs do not have the midrange OK. Get a decent carb like Webra, MVVS or OS. An Enya also is good, but the very narrow midrange slit fouls easily.
If the engine is an MDS, clean the spraybar and needle very well. There also is a hardly visible slit there (in the idle needle) that controls the midrange.