Sasboulder

I change the oil on my Cayenne at 5K max, oil changes are the easiest and least expensive way to keep your car on the road. 

The best way to know for sure is to remove the plugs and borescope the cylinders (with the pistons at the bottom of the cylinder). 

I would recommend a rebuilt unit that has been balanced after rebuilding. I have seen that rear unit begin to fail and that can cause vibration also. Colorado Driveshaft in Denver, CO usually has them ready to ship, and I've installed at least 20 of their units without issue. Good Luck! 

Was that code setting before replacement of the vacuum pump? Probably a good idea to smoke test the intake and see if/what's leaking vacuum. Or is the sensor wiring good, fully seated connector etc. 

SOMETHING I FORGOT TO POST, the way we figured out the inner bushing was bad was the exaggerated wear where the seal goes, even though our converter had some wear where the seal rides, we polished it and with the torque converter being held steady again it hasn't leaked in 35K miles (this was about 5 years ago). 

Hi, 

I have run into this issue, we had a local aerospace machine shop bore out the torque converter and press in a bronze sleeve. Then honed sleeve out to original size, and off you go. The reason this one failed, someone replaced the transaxle and didn't notice one of the locating dowels stayed in the old transaxle, the result was a repeated failure of the torque converter seal and damage to the bushing. 

This repair worked well for us, but we did fab a custom plug to keep all those nasty machine shop bits out of the torque converter,  autos are VERY cranky when filled with lots of small, hard debris! 

Good luck