Problem to Start Engine

When a tryed to strat the engine I need to do taht like three times in the first time sound like explosion and in the other chances sounds like air exhaust.
This happens when the engine is warm or litlle warm, for example in the morning in the first time the engine started perfectly
I read here that could be the Fuel Pressure regulator.
My problem could be related to this also?If yes, where is located the FPR?

CAR INFO: IMPALA 2001
ENGINE: 3.8 or 3800 series

First of all what year, what engine, basic info is missing!!!

That exact issue is expressed here: http://www.automotiveforums.com/vbulletin/showthread.php?t=696650

Good the issue is, but again what car and year, part of the forum rules still no info!

Sorry for the mistake.
Car Info: Impala 2001

What engine??? Please, you are wasting our and your time here, 3 posts to get the info!

Engine 3.8 or 3800 Series

Look for fuel in the vacuum hose to the pressure regulator it is at the end of the fuel rail under the engine cover, remove the cover to acccess.