All I needed to read was the first few lines to guess OS with the rear needle. Some of those things produce their own bubbles at the needle. Have no clue as to why. I went through a couple 91 FX engine and never got them to work. Some guys are putting fuel line over the needle to the housing to stop it. You can also try a K&B needle to see if it solves it. Make sure the bubbles start at the carb before playing with it there. If there are none coming from behind the firewall and they start at the remote needle, then the problem is there. I found it easier to just go to an engine with the needle in the carb where it belongs. No more problems.