i just dropped the tank to put in my new BBK 255lph fuel pump, and now every time i start up the car the gas guage hangs at E for like 10 minutes of driving then slowly starts to climb up.. this is a new combo so im not sure what kind of mileage i'm going to get with it, so i cant just go off of the amount of miles i drive and then fill up, i need to be able to see what levels its at.. what could i have messed up, or what could have gone bad to cause this problem?