On the way to work today I sat quite a while at a light and punched it when I had a chance to go. Got the tire to spin a little around the corner which surprised me a bit since it seems pretty sluggish.
As I came to the next intersection and slowed for the light I noticed it was running very rough. I proceeded the next mile to work and now I'm loosing vacuum since the brakes hardly work and it just about dies when I get to a stop. It boggs hard until I get RPMs up to about 1500 and then it smooths out.

1st... I'm going to do is unplug the PCM to clear any code or values that might be stored and causing the problem, though I do not show an SES light.
2nd... I will check timing tomorrow to make sure the distributor clamp was not loose and I spun the distributor when I took it WOT. Something I have not done since replacing intake gaskets.

I am posting this in case there is any reason I should worry about having lost a head gasket. Is that common on the 4.3 or are they fairly stout and can take some abuse? Is there anything else I should make sure to check while I'm at it? I'm definately leaning towards a timing related issue due to the way it acs but anything is possible.

 

Your head gasket is fine. I would guess you opened up an old brittle vac line when you WOT'd it.

 

Sorry, I pulled out the Jump to Conclusion mat a bit to early. The EGR had stuck open apparently. In my attempt to limp home it cleared up as soon as it got to what I would estimate by the gauge to be around 150*. SES showed up during limp home attempt but has since cleared today when I started it up again. I do find it interesting that the EGR opens when at high throttle? That doesn't seem correct since the old stuff would shut EGR off after something like 75% throttle. Guess that's some good winter research.