fuel economy

was looking through the economy report post and found something about replaceing the cpi unit and fuel lines
now im geting about 9 or 10 mpg on highway i have a 99 4x4 4 door
my question is how do i know if this is my problem and how much is it in price and work

The cpi was used on 95 and older VIN W 4.3's. The regulators and fuel lines were prone to leaking. What you have is a CSFI unit, found on 96+ VIN X and W 4.3's. It looks similar to a cpi but functions differently. They are prone to having leaking or clogged injectors. Any drivability issues? Have you performed a tune up lately (cap, rotor, plugs and wires, fuel filter, air filter)? Have the O2 sensors ever been changed? If its an automatic, has the fluid and filter been changed? If its a 4x4, make sure that it is not stuck in 4wd.

did a plugs wires cap rotor air filter fuel about 300 miles ago
it dose have a slight hesitation on hard exceleration sometimes it will even pop through the intake other wise it drives good
also did a fueel pump about 5 months ago
its is an automatic it is not stuck in 4wd the trans fluid was changed about 20,000 miles ago along with a shift solinoied dont remember witch one but it dose shift good all the way to over drive

Checking fuel pressure and leakdown rate will tell if you have any problems with fuel delivery to the injector. Ignition on, engine off, fuel pump running, pressure must be 60psi to 66psi. Must remain above 55psi for 3 to 5 minutes after the pump shuts off.

If leak down remains above 55psi, the injector, "nut Kit" (lines in the plenum), the fuel pressure regulator, the lines from the pump, and the check valve in the fuel pump are all ok.