lately my 85 firebird has been feeling alittle sluggish from take off so i took it to get looked at. the shop said that when they hooked their diaganostic machine up to my computer it wasnt responding . they said i may need a new comptuer . could this be effecting my perfomance of the car that much ??

 

It's more likely that their scanner isn't compatible with the old low-speed serial data connection your ECM has.

 

maybe i will take it to another shop ... do the computers on these older cars really control much i thought newer cars the comptuers played a bigger role

 

It doesn't control as much as newer cars, but it controls enough. If it's not setting codes, you're probably not going to get much useful data from the computer anyway, you're probably better off troubleshooting it the old fashioned way.