If he did the mosfet mods exactly as they're laid out on cbtricks.com, then you wouldn't have such a low key. it sounds to me like your tech did something else he probably shouldn't have. Look at L17 (square can) just in front of the driver's mounting location. Right in front of that is JP32. If that looks like anything other than a simple 1/4"-long wire jumper running from left to right, then remove whatever is there, and replace it with a simple wire jumper.
Also look at JP36 in front og the final. It should also be a simple wire jumper. if it isn't, remove whatever is there and replace with a wire jumper. JP36 runs front to back, from right at the corner bend of that heat sink back to the hole just 8in front of the final bias resistor.