TAP chip for S4

[Robin Gates <72355.650@CompuServe.COM>]

I just bought a 93 S4 this week (Thanks to everyone who has given me leads and
advice over the last year).  I found out after I bought the car that the
previous owner had installed a TAP chip a couple of months age.  I would like to
know if this is a well respected chip and whether I am risking any damage to the
car by using it.  I have the original chip and could have it reinstalled.  Also,
does anyone know how the chip affects extended warranties.  The warranty itself
is not precise on the issue of chips.  Any advice would be appreciated.  Thanks.