Just got a Walbro fuel pump installed 2 months ago, and had everything cleaned out nice, new filter and all. Just recently though I am having problems with the RPMS dropping when your doing about 75ish. If you burn rubber and really push it from a dead stop it is fine infact it is better than ever you can push it to 4 grand and then pop it into 1st and it will sit there forever burning out on brand new nittos so I know it isn't a power problem....no probs.....and if your doing 110 plus it is fine, but for some reason it slips around 65-80 doing everyday driving and out of nowhere the RPMS drop an it sounds like it is struggling. The belt in it was REALLY bad, so I changed it 2 days ago hoping the belt was slipping and just causing power loss or something, but no go. Some one metioned a multi spark to me and that it may be the probelm. Any one know anything about it, or have any suggestions on what it could possibly be? ANY HELP IS GREAT!?!?!

 

Um, bad ground connection to the new pump?

Just a shot in the dark.

 

Does it hestitate a bit when you first punch? I wonder if the fuel line between the pump and the top of the tank came off, even just a little bit. What happens then is that the engine will be starved of fuel at first and then the pump will literally spray fuel up into the hose and then it will get to the engine. Have someone start the car up and place your ear on the hump above the fuel tank and see if you can hear gasoline spraying or splashing inside the tank.