198 surges at partial throttle cruise

Repeat; post #22
#1)Start with the Accelerator pump circuit. The check balls may not be working, or the pump is faulty, or the nozzle restricted,faulty adjustment,or simply just too much slack or slop in the linkage system.
#2) Set the T-port sync (see below)
#3) Crank the metering rods up, if you got such. If no Mrods, raise the float level 1mm at a time.
#4) If you still got problems, you are gonna have to disassemble that baby and go through the emulsion system.