i have a walbro fuel pump, straight 12v wired.

i was waiting for a friend outside of his house, as i idled outside then i turn on the emergency flashers, everytime it goes on i hear the fuel pump weaken then when lights off it goes back to normal, and it does this while the e-flashers are on. Is this normal?

 

Perfectly normal. Your lights are drawing some of the current that would normally keep the pump spinning.

If you have underdrive pulleys, you typically here the pump drop at idle vs. higher rpm.