Here’s a great article by Dirk Wacker that has been online for a while over at http://www.premierguitar.com. It’s basically a discussion of the most popular mods that can be performed on your good ‘ole Tube Screamer – op amp changes, fatness mods, tone shifts, clipping options e.t.c. Here’s the link, check it out: http://www.premierguitar.com/Magazine/Issue/2007/Jan/The_Ultimate_Tube_Screamer_Mod_Guide.aspx