buzzing sound when accelerating

[Heinrich]

Hello fellow Members,
I have a '99 VoIvo S-80 T6. I recently had a total valve job done for having burnt the # 5 E Valve. Ever since I picked up the car there is s strange buzzing sort of sound coming from around the instrument dash or top of the steering column only when accelerating. The car otherwise runs fine. I can not seem to pinpoint this buzzing/hum sound while accelerating.?? Any advice would be appreciated.
Sincerely,
Heinrich