that's my next step, when the weather decides to clear

 

UPDATE:

So after a long rainy season and the weather finally getting warm, i put off my truck problem and started driving the Jeep and riding my motorcycle more. After checking everything previously stated in this thread, my last step was to see if the cat was clogged/going bad. An exhaust backpressure reading showed it was good.

I started by having a random misfire code for cylinder 8. my symptoms overall:

1) p0172 code
2) shuddering around 35-40 mph
3) CEL would blink at WOT
4) sitting idle, i would experience surging-the truck would want to "jump" sometimes.
5) exhaust note just didn't sound right, lopey idle at times.
6) very poor fuel mileage

I replaced:

1) plugs, wires, coil boots (noticed plugs on Cyl 8 were a little dark. changed them 3 times over a 9k mile period and it progressively got worse on that cylinder).
2) crankshaft position sensor
3) both o2 sensors
4) PCV valve
5) returned my cheap "cold air" intake back to the stock set up with a quality paper element filter.
6) cleaned throttle body many times.
7) made a primary ground wire for the throttle body itself.
8) replaced #8 coil and fuel injector

I would notice a slight improvement (placebo i think) and eventually return to the symptoms above. So, after all these steps I knew the inevitable had to happen. I started with the cheapest/easiest to get to parts and saveed the most invasive for last which in hindsight would have saved me some money. I removed all the associated parts, off comes passenger side valve cover...............

 

#8 valve spring (exhaust side).

$16 at the dealer.

runs like a Hemi now and fuel mileage almost doubled in town.


thanks for all that gave input