Hi, I've been a Volvo Tech since 2005. Master for the last 3 years. Sounds like a MAF is on the way out. Especially if you get no codes. Coils shit out all the time, but set fault codes. There is an alph numeric code on the coil tops for date of man. to roughly date them. If they are original might as well replace them (all) while you are in there. To clean the throttle there is onle the old fashioned take it off and degunk on the bench. (unlikely the problem). Good luck!!! I'll keep an eye peeled here for progress.
"I can't believe I threw up in front of Dean Wormer!!!! Kent, You threw up on Dean Wormer"