I just bought a 1989 ford f350 crew cab 2 WD with a 5.8L engine. It starts fine and runs fine but when I come to a stop it will idle fine for 5-10 seconds and then start cutting out like it is going to die. Once I get under way again it seems to run fine while moving down the road. No misfiring or anything. I am thinking it is starving out of fuel at an idle. I purchased a $10 in-line fuel filter but do not see an existing filter along the frame rail under driver side area. I found the fuel pump and followed the lines but cannot find thefilter location. Where should I be looking?

its fuel injected?..its either on the frame...or in the tank