Ahh. Yeah i dont plan to pull the valley cover unless i see a problem once i get in.

 

Yup. The insulation on the harness can get brittle due to heat. The connectors on the harness also get weak. The knock sensors themselves -- same issue. If you try to pull the plug off and not be careful the plastic can crack. Valley cover gasket and knock sensor seals probably aren't needed but it is one of those things you think about more when you get closer to joining the 200 000 mile club.

The intake manifold seals ARE a good deal. I have seen plenty of those leak

 

I replaced the MAF, and pcv valve, Cleaned the the throttle body, and sea foamed the intake with half a can, and put other half in the fuel tank. Truck is running better, but still seems sluggish, and the p0101 code came back. What would the next step be?
Knock out the cats? Looks like a super hard job without having a welder.
Any other sensors I should look at?

 

Was it a New MAF or a remanufactured one???

 

It was new

 

So was it a big difference in power with a set of working knock sensors?

 

yes. before it felt like a 4.8 trying to pull a 3/4 ton truck if I stomped it from a dig...it made a hollow noise and slugged out there. now it is a ton more responsive and will actually turn the tires on dry pavement with 33" tires. before the new senosrs/harness it wouldn't turn the tires on a wet road going up hill. I wouldn't be surprised if the MPG improves too.

 

Good job on getting it fixed

 

Should I only worry about the knock sensors if I have a code for them? That seems just like what my truck is doing.
For something advertised as 285 tq. I would think it would be able to spin the tires at least in gravel. With no load, it has to shift into third to pull a slight hill, it's actually pretty sad. 15 sec 0-60 time???? Really????

 

Also, I had a. 04 Yukon xl with the 5.3. It quit running on my wife wile she was on a trip (400 miles from home) find out the cats were plugs smooth up. They said to replace the manifold gaskets, so I did, but turned out the intake itself had a crack in it. Is that a common problem also, other than the gaskets leaking.
Chevy tech said that the crack "seals up" during idle, but when at WOT the crack opens up and really leans out the motor causing the cats to melt.