Michael,
I wonder if you might have a bit of RF floating around that is 
confusing the issue and perhaps giving you false meter readings?
Since it is band specific it might be the case.
Maybe a slightly different length of coax between the rig and linear 
would change things; perhaps a little different grounding.  It's all 
a big experiment!!
Pat, K9JAU
p s  Thanks for the info on the Yaesu.  Good knowledge to have.At 
07:35 AM 4/18/2010, you wrote:
>Hi List:=20
>
>Last night on 40m, I experienced a puzzling with my Amp.=20
>I tuned up as normal and with 65W of drive, amp in the CW/Tune, I got =
>840W out as normal.=20
>When I decreased my drive however, the output increased. 59W showed =
>905W.=20
>My initial 10 starting tune up, showed 240. Now when I 1ST bought this =
>old beast, the Gentleman who gave the amp the once over for me told me =
>that the meter may sometimes stick and I'm wondering if that was one of =
>those times.=20
>On 20M this afternoon, everything went normal, 100 in, 1000 out in the =
>CW/tune, 840 with 65.=20
>40M seems to be the only band on this amp that gives me an occasional =
>puzzling. Maybe it's haunted? LOL=20
>
>73:=20
>Michael DE VO1RYN=20
>
>P S=20
>Love my FT-450. I pulled a VK out of the noise last night on 80M with =
>the filtering, with a carolina windom at 35F.=20
>Couldn't do that with my other rigs. Note: when in split, the vs =
>announces both freqs with out holding the TX watch. =20
>It says: "RX freq # plus mode then TX  freq plus mode.=20