I cannot see the fuel tank location from the pix's, I believe you are flooding out on idle ,because your carb fuel inlet is now lower then your tank. Instead of drawing fuel you are now siphoning. At higher speeds, no problem. My problem is tuning for level fight and in a nose up aditude goes lean.
, tune for nose up aditude and level fight is rich. Reason: In a straight line from clunk to carb is 10 inches add the extra fuel line to attach the fueliging point 2-1/2 more inches for a total of 12-1/2 inches of fuel travel. Even for a G90 thats alot of pulling and thats why I ordered a perry pump. Most manufacturers only recommend no more then 7 inches total to carb.

Mike