I just got a high flow 255LPH walbro fuel pump. I have two questions.
1. do I need a fuel regulator with this fuel pump? and
2. does the tank "have to" be nearly empty to do this or is it just easier?

 

Technically No. I'm running a Walbro with the stock FPR (and colder plugs) and I'm still getting 21-22 mpg. You just have to stay light on the throttle and stay OFF of WOT. The car will have a higher fuel pressure across the board, but the O2 sensors should adjust the injector pulse width to compensate. If you're really concerned with power/gas mileage the FPR is worth it because you can adjust the baseline and WOT fuel pressure.

To give you an idea:
Stock baseline PSI is 34, WOT 43
Walbro baseline PSI 40, WOT 50

At WOT the car pretty much runs a straight fuel map and doesn't adjust the injector pulse width, so you're using the stock pulse width with 7 more PSI of fuel which should leave you really rich. I should be dynoing soon, so I can tell you exactly how rich.

You really should be at about 1/4 tank or lower. This will help minimize the gas you get on you and will make the experience much more pleasant. If you have the option, work outside with both rear doors open to minmize the fumes.
-hype

 

will it hurt my WOT performance if I do not use a new FPR?

 

also this is a high flow not a high pressure. does this matter?

 

Yes it does matter. Sorry, I assumed you meant a Walbro high flow HP pump since thats what most people get. With the 255lph high flow you should be fine as far as fuel pressure goes. Any reason you got a 255lph over the 190lph?
-hype

 

it was free