2003 V70 - "pulsing" under accelleration/load

[brian2468]

Hi all....need some help - running out of ideas!

2003 V70 2.4 NA/Manual transmission - 135k miles

Car has seemed sluggish for a while - also feels like it is pulsing or surging when accelerating hard or going up hills. Idles smoothly and runs fine under light load.

Have replaced MAF sensor, air filter, and fixed a couple small vacuum leaks. Also had fuel pressure sensor changed under a recall. All of these things improved performance but problem still there.

Changed plugs - originally used Autolites - pulsing was so bad the car would barely make it up a small hill. Replaced with new Volvo plugs and is now running MUCH better. But still intermittently pulsing under hard throttle. Because of the difference with plugs I suspect I may have an issue with coil packs. Bought 1 new coil and have played musical coil packs, but pulsing/low power still there, though not all the time - sometimes car runs fine.

Have P0441 Evap small leak code, and P0420 catalyst efficiency low bank 1 codes.

Was thinking that I should change the other coil packs. Any insights?? Or should I give up and bring it in to be fixed?

Another maybe related question - what is the vacuum solenoid for on the left side (standing in front of the car) of the intake manifold behind the PS pump? I assume something for the PCV/oil trap system. Maybe another vacuum leak there?

Thanks!!!

Brian