Runs rough up hills.

[Washi]

I have a 1999 Ranger 3.0 Flex Fuel 4x4 auto. Ever since I've owned it (bought at 115,000 now 140,000) I've noticed a shudder just before it down shifted going uphill. Now going uphill it feels like it starts to miss or the tranny is slipping. From what I've read on here it is most likely not transmission related. In fact I've seen several threads on here where people had the same symptoms but they rarely come back and say if or what fixed their problem.
The codes were PO401 EGR flow insufficient, and PO320 IGN/DIST engine speed input circuit. A new DPFE sensor got rid of the CEL but it still runs the same. I'm not sure what might cause the PO320 so if you could help me there I'd appreciate it.
Oh and I also read here that it's a good idea to remove and clean the EGR valve and sensor but I have no idea where it is and my Haynes is no help. A description AND picture would be awesome.
Wow that's long. Thanks in advance for any help.

 

[Big Jim M]

Does it miss at high speed in passing gear? Flow insufficient could be as simple as a fuel filter.. Stumbleing at speed when more power is needed could be worn plugs that need regapping to the correct gap..
Big JIm

 

[Washi]

It mostly happens when I'm running along about 65-70 and I go up a hill. It seems to get worse towards the top of the hill. It seems like if I get the RPM's up I don't feel it. I've only noticed it once at slower speeds (about 35mph) but I was going up a pretty steep hill.
I'm getting the spark plugs and wires, fuel filter, transmission fluid and filter, and a bad ABS sensor all replaced this week. It's all stuff that needed done anyway.

 

[Washi]

Damn now today it didn't do it going uphill but it did do it on a flat stretch of road. Luckily I'm dropping it off tomorrow to get it worked on. I'll let you know if it helps.

 

[Washi]

I almost forgot to come back with an update. The day I dropped it off it was running pretty rough. After the tune up it runs like a champ. I guess the plugs and wires were just that old.