Changine performance

This is an odd one for me. I had my car dyno'd. Its a 1994 z28 with 180k on it. Valve covers have never been off. It gave 180rwhp the 1st pull 250wrhp the 2nd pull and 225 the 3rd pull. Ive noticed on the road that, even though the temp is the same, the acceleration varies from 5.5 all the up to past 7 seconds 0-60. Any idea on this? Also, My friend has removed the spring on the thermostat, I plugged my snap on scanner into his OBD port and the car is running on average 140-160*F. Is this ok to do for my car too?

Usually they run a little hotter than that, Did you have your fans reprogrammed Also do you have a Auto or 6 speed

is the z28 stock layin down 250? no mods?

Also, My friend has removed the spring on the thermostat, I plugged my snap on scanner into his OBD port and the car is running on average 140-160*F. Is this ok to do for my car too?

Not a good idea.. doesnt sit well with a/f and emissions

its automatic... and to be honest i did the same thing with the thermostat.. and its actually running alot more colder, and powerful.

i dont know why you would pull such different numbers three times...

If you where having a ignition, Fuel injector or pressure or compression(most likely not the case) or Vacuum probelm. The results could be drastically different each run.

Not a good idea.. doesnt sit well with a/f and emissions

I agree, these cars run best between 160 and 180. 140 is way to low.