2007 GMC Sierra 1500 SLT 5.3 4X4


I'll make this short and to the point, P0420/430, P0171/174 codes. Replaced the downstream 02 sensors, ran some cat cleaner through it, buttoned up the air intake box (dealer left the screws out when they had it for some reason). Also when I start it it stumbles a bit, but when warmed up it settles down. And when I first drive it in the morning I get traction control/stabilitrak off, and service traction control/stabilitrak only when I slow down. When I start to accelerate it shift hard for 1st to second then goes away. Bit in the afternoon when I leave work it'* fine. I'm going to replace the fuel filter this weekend, reset the code and do a few drive cycles. Hopefully it'* not my cat(*). Any words of wisdom would be much appreciated. I've done extensive research and just curious to what ya'll have for me.
Also had had the wheel bearings/hubs, cv axles, control arms, rotors and abs sensors replaces a few months ago

Prepare yourself to replace the cat. Those cat cleaners are a joke.
How have you determined it needs a new fuel filter?
Do you believe in testing? Do you have tools?

The 171/174 code says its too lean. So either too much air or not enough fuel.i checked for vacuum leaks of anywhere it could be sucking air, found none. So now im going to see if the fuel filter is clogged and if so I'll replace it. Yes I believe in testing, and yes I have tools.

I'd spray around the intake rather than listening. Does your scan tool do all modules, live data?

No, it'* just a simple bosch ODBII 1000. What am I spraying. I just looked around for loose hoses and such. Could possibly be my MAFS?

How many miles on it?

How many miles have you owned it?

Bought it with 224K, currently has 240K.

P0171 - Bank 1 too lean
P0174 - Bank 2 too lean
P0420 - Bank 1 catalytic converter below efficiency threshold
P0430 - Bank 2 catalytic converter below efficiency threshold

240,000 miles

I suspect low fuel pressure caused a lean condition which created a hot mixture and put the very tired catalytic converters over the edge and they gave up.

How many miles has the check engine light been on?

What is the fuel pressure at idle?

Not sure what the fuel pressure is, dont have a tool for it. As far as the check engine light, I wipe the codes when I think I've fixed it. Installed a new fuel filter and still have to do a drive cycle or 2. The drive cycle is near impossible unless you have access to a track for a portion of it. I'll probably pull the cats and check them, they may be shot.

Very cheap fuel pressure gauge needed. You can borrow it for parts place but for less than 30 clams it'* a very needed tool if you are going to be working on these.
Spray carb cleaner around the mating surfaces of the intake. If idle changes you found your leak.