If it's missing and also lacking power, I would suspect the mass air flow sensor. I've also seen the O2 sensors cause problems like this, but you'll normally have trouble codes with these. Usually with a bad mass airflow sensor you'll have codes as well, but with this system, you may not.
Did this problem occur right after doing the 45,000 service, or did it take awhile? Or was it doing pretty much the same thing before the service? Were the plugs replaced during the service, and if so were they the proper (Bosch F8DC4) plugs?