91 sl trying snake eye mod

Im trying the one wire snake eye mod(http://mi3si.org/techdata/mysnakes.htm). After placeing the jumper wire in the sockets about 30 seconds later both of my suspension lights tour and sport begin to blink. And when i turn on snake it lowers my roms from 700 to about 500. Has this happend to anyone with a 91 SL. Thanks in advance also if anyone has the snake eye mod on a 91 what method did they use.