fuel issue after car sits.

I ran across this thread a while back and decided to check back to see if the issue was resolved....I too have just started having this issue with my slant ( for the last couple of weeks ).
Previous starting method was pump, pump, crank done.

Current starting method: crank, crank, pump, pump crank, cough, sputter, almost stall... Pumping the pedal before cranking will fire the engine but will immediately stall

Mine is a daily driver so it happens overnight, and goes through a tank every 8-9 days so old gas shouldn't be a problem. I have replaced all of the rubber line in the fuel system with injector line also.

How would one go about testing the check valve in the pump? Could I just take the line off of the carb and blow into it to see if it's allowing pressure back through??

In regards to the "fuel formulation" topic, I've found some interesting reading....
http://www.zhome.com/ZCMnL/PICS/winterGas/winterGas.html