Uneven balance

I am experiencing uneven balance between the speakers. After switching speakers, the left channel continues to produce more volume that the right. The pre amp and amp are tubed with new tubes all around. The preamp recently serviced and the factory gave the pre a clean bill of health. Any thoughts would be appreciated. Thanks.
Due to room accoustics my right speaker is louder in my listening position than the left, I use the balance, would prefer a better room but the balance works.
I'd suggest following Davt's lead and look at your room configuration. Asymmetry can be a problem, especially with speakers that have a wide dispersion in rooms where the primary reflection points are different from the left side to the right. That can really skew the stereo image.

If that's the source of your problem it can often be improved by experimenting with speaker placement in the room and acoustic treatments.
Have those new tubes tested with a tube tester(unless they were already tested/matched to begin with). The transconductance of your tubes for the right and left channels in your preamp and/or amp might indicate a considerable difference or mismatch. If this is the case it might explain the difference in perceived output you hear between the right and left channels. This is not an uncommon occurence.
I agree with Opus88.
Check your bias settings. If there off due to re-tubing, it will cause the ballance to be off.
A quick way to check if it is the tubes, assuming biasing et al is not fast and easy, just switch the speaker cables at the amp (only) and obviously just for testing. If it is the tubes, the opposite speaker will start sounding louder. If not, it sounds like it is a room placement/acoustic issue. Of course, it is assumed that the speakers (cross-overs) are not presenting the issue and that you already checked this.
Thanks for all of your responses. You guys were right on. A simple removal of wall treatments made the new Audio Physic's sing.