2004 - XC70 - 225,000 miles - has newer fuel pump - after the car has warmed up it feels like there is something weighing the engine down as if there are extra AC condensers turned on. there is a barely noticeable vibration on the throttle pedal that accompanies this behavior. car is throwing no codes. fuel pump, alternator, and ac condenser all ok. shifting fine. it had been throwing a catalytic converter code 6 months back, I thought it was maybe a clogged CC, but again no codes currently. maybe the MAF sensor??? it is possible that the sparks plugs need to be swapped out??? looking for an assist, this one has me stumped.