2000 S80 T6 ETM or transmission or vacuum leak?

[jkdjim]

I need to finally address some issues in my car and I don't want to pay for a mechanic who doesn't fully understand my issues. I have a Volvo guy, but I'm a little reluctant to use him again as he's often too busy to call back and has overlooked some issues in the past.

Here are my main issues and I think they might be related:
-Car doesn't like to rev past 2000rpm. It will if I really gas it, but that's where he likes to stay most times.
-Dies when in stop and go traffic on freeway. Usually I'm coming to a stop or I'm just idling, but it recently happened going slightly downhill and I really didn't like that.
-Brakes feel funny. I posted before concerning the hiss coming from the pedal area and it was concluded that the brake boosters go bad.
-Crappy mpg. I think the best I've ever recorded is ~17mpg. I tend to get 15-16 with a lot of city driving. I can get the instantaneous to stay around 21-23 when cruising, but once I'm off the freeways, its quite low.


I have to pull codes and in the past there was one about a potential vacuum leak, but that was some time ago. Car has 148k miles. Purchased with 113k. PCV might need to be done, but I think I was good (no inflation of rubber glove) when I tested. Fuel filter was changed when I first got the car, but some people say that could cause bad acceleration. I just think the brake booster might be connected with a vacuum leak, but I've never checked for leaks before.

I would sincerely appreciate some direction on where to start, especially if someone has had a combination of these in the past. Smog is due in a few months so I don't want to pay too much in parts (ETM, PCV) if I can't pass smog.

Any help would be greatly appreciated.