i installed alluminum underdrive pullies on my 4.6L i have had trouble getting the car to stay running. i thought it could be a fuel issue but i replaced the fuel filter and the pump is working fine. could it be something to do with the pullies or is this just a coinsidence?

 

The battery could have a weak cell and/or the generator could be tired--either of those conditions could have been aggravated by the UDPs...