If you want to add a little gain, there is a simple gain mod. I'm trying to remember the tube... maybe v4 (might have been V4 on the Mark IV, so translate it to the Mark III?. Either way there is a 68k going to ground. Replace it with anything bigger up to 150k. It will be like making the gain pot go up to 12 (vs 10). It will make the amp slightly darker is you use a 150k... but its a mesa and they can be bright already. This mod came directly from Mike B.