RE: SAP 180 (Syssa Performance)
yeah, sounds to me like its a fairly peaky engine and therefore not suited to pattern.
I guess you could re-jet the carb to provide more consistent fuel feed across a broader rpm range but then you better know what you're doing.
Have you tried a DLE30 or RCGF 32 or Mintor 33 or Evolution/MVVS 26/30cc in that plane?