In my dad'* silver (he also has a white one) 1989 Lesabre I borrowed befoer I got my SLE I saw 120 (this car was a Limited and had the upgraded guage cluster which read 120). I had the GPS along on a few occasions and that gave readings of 121 and once I even saw 124mph. Not bad for the poor machine as it had 230,000 miles on it. Good testimony to the realiability of the L27.
Here is a pic of the top speed I achieved with the GPS in my 1994 Bonneville. I've had it at higher speeds with the GPS but never took pics. The highest I recall was 122. The speed governor kicks in only when it wants to it seems.
After I installed the Superchip the fastest I could ever achieve with on GPS was 102 (Superchips are not worth the time of day).
I feel when I had the Supechip in it messed something up as after I swapped the stock computer chip back the best I could achive was about 112 and after 95 it takes forever.