97 5.0 sierra bank 1 bank 2 rich

i have a 97 gmc 1/2 ton with a 5.0 and i keep setting po172 and po175 at the same time. i have changed the fuel pressure regulator and both primary o2 sensors but the codes keep coming back. i have also cleaned the maf sensor to no avail. please help.
i am about to suscribe to alldata diy for help

The vortecs use central port injection so you may have a leaking injector causing you to run rich.

There is an updated assembly that converts from central SFI to Multi-port FI (i.e. 8 injectors instead of one). The cost (looking at www.rockauto.com) is a little over $300 for the updated assembly.

//2000CAYukon

here is an update
Went to harbour freight and brought a cheap fuel pressure tester and low and behold after a five minute leak down test the fuel pressure dropped at least 8 psi (57 psi to 49psi) so it looks like i have a leaking injecting.
i just need to figure out if the mfi conversion kit will work
will keep updated

Keep in mind that if you did not isolate the injectors from the fuel pump, you could have a fuel pump bleeding down inside the fuel tank, causing your 8 psi pressure drop. Have you checked your air filter for restriction? Your MAP (manifold absolute pressure) sensor also plays an important role in fuel delivery. If the MAP sensor is not connected to the intake manifold properly, or has a vacuum leak (or any vacuum leak for that matter), the pcm may think you're running at or near wide open throttle. The pcm translates it this way: less vacuum = more fuel.
The fuel injector kit is available because the fuel quality in california is so bad that the little "poppet" valves as they are called, get plugged and cause misfires/lean running conditions. This setup (what you currently have) has 8 injectors. They are located centrally at the top of the plastic intake plenum. The square black connector with 16 wires in it plugs directly into the injectors. This spider assembly (inside the intake plenum) has tubes that run to each cylinder from each injector with a poppet valve at the end. That would not cause a P0172/P0175 to set if they were plugged.
This "conversion" kit being talked about fits in place of your existing injectors. The only difference is that instead of the injectors being at the very top of the intake, they moved the injectors directly to the cylinder's intake port, eliminating the poppet valve at each cylinder.

thanks for the info.
my line of thinkg kinda goes like this, i performed a static fuel pressure test first(koeo) and i did not notice a fuel drop until after i turned the key off and the pump stopped.
i also checked all the vacuam hoses and did not notice any cracked or broken hoses.
i will list all the parameters my scanners sees when i set the cel again
thanks again everybody

i am back and still getting the same codes
i can reset the cel and drive all day and as long as i do not shut the engine off the cel will never come back. but as soon as i shut the engine off and then start it back up the cel will set in a very short time
so i have stated to think that it might be my prom acting up
any ideas

Have you checked your EGR valve ? If there is a piece of carbon keeping the plunger open this could cause the rich mixture codes.