As you probably realize, the 4004MkII is rated at 200W and 400W into 8 and 4 ohms respectively. At the time it was introduced, FTC requirements for amplifier power ratings specified a "pre-conditioning" prior to the measurements, comprised of 1 hour of operation driving a 1kHz signal into an 8 ohm or 4 ohm resistive load, at 1/3 of rated power. I believe that about 10 years ago the pre-conditioning requirements were revised to something less stringent.
I would question the tech as to how he did the pre-conditioning. If it was for longer than 1 hour, or at more than 1/3 of rated power, that might account for the 4 ohm measurement being less than 400W.
Also, I would ask him what the temperature conditions of the room were at the time. In a hot, non-air conditioned environment it is also conceivable that the measurement would be reduced.
Regards,
-- Al
