My wife has a 2003 Saturn ION2 with 2.2 Ecotec
Her dad has a 2003 Cavalier sedan, 2.2 Ecotec
both are 5 speed

When i drive the Cav, everytime it feels like it's got so much more power.
Yet the ION has a plastic body, so it should be lighter and therefore accelerate faster, should it not?
why is this?

Is there a difference in tuning?, Tranny? or is this all caused by the A/C in the ION vs no A/C in the Cav?
What would I have to change to get the ION to be just as quick as the Cav?

It is most likely just the ECU tuning. I have noticed the same thing between my 2003 Cav and my girlfriends 2005 Sunfire. My car has a faster 0-60 but her 60-100 is WAY faster.