On these particular fuel systems, fuel volume is more of an issue then fuel pressure. My recommendation is to hook up a fuel pressure gauge on the pressure line and pinch off the return line (a rubber part of course). A significant rise in pressure should result! If it does not, the the fuel pump is weak and needs to be replaced! A lot of times guys hook up the gauge and just look at the pressure and its within specs so they think its ok. But that cant figure out the run problem! Just something to keep in mind!
As far as the idle problem goes, U might have an air or a vacuum leak. This is very common! Open the hood and listen for a hissing sound when the engine is running. If it is hard to pinpoint take some break cleaner or starting fluid around the intake manifold and vacuum lines and see if the engine stumble or if the idle is affected. Be extremely careful when doing this!
If this has helped in any way, please hit the ACCEPT button. If my answer is unclear or if u need more info, just ask! Thanks! 