Hi Poolman, Thanks for the replies. I will look at the vacuum hoses etc, but it doesn't feel to me like a vacuum leak (also, the climate control and brakes are working normally). I replaced the temp sensor a couple of weeks ago due to a haywire temp gauge and cooling fans, but that had no effect on the miss. I would describe the miss not as a dead miss, but more as a partial miss on more than one cylinder. The engine just isn't smooth the way a straight 6 ought to be, and it seems to be getting worse. Power also seems to be down. I am not suspecting the AMM or CAS because they would affect all 6 cylinders equally, I think. Do you have any more info on the power stages? Do you recommend dismissing the coils as possible culprets? Plugs have <20K miles on them (Bosch Cu cores) and look good. I will replace them anyway next time I have the coils out. Air filter is clean. Thanks for your thoughts. Tom