I just picked up my first pedal in years - a ZVex Wooly Mammoth. I owned one of these many moons ago, before they made the change adding the LED and the 9v power plug. Now that I've had time to sit down and try it, it seems different than my old one. It's a lot less gainy, and a bit darker, from what I can remember. I remember that even at the lowest gain stages it would break up quite a bit, yet this one has almost no gain at it's lowest levels. It also doesn't start getting really buzzy until the gain is way up, which is quite different from what I remember of the previous one. I still like the pedal - perhaps now it's even more versatile than what it was before. Is this my imagination and/or faulty memory, or has it actually changed?
From talking to Mr. Vex, the pedal should be the same. The only thing that should have changed was the paint job as well as the LED, which will not have any effect on the sound. Since it is Chuck Zwicky's design, it hasn't changed. Whats more likely however is that since this is a transistor based fuzz, each unit will have some tonal variance, so you probably got a really hot one the first time and a more laid back one this time. This is of course not to say that yours is mild, as this pedal would drive a rabid rhinoceros away. Just my .02 cents. I love love love mine.