car pulsates under load when in power mode

[zr1man@yahoo.ca]

I just bought a 1991 corvette zr1 and i dont find any difference when i switch from normal to power mode. in normal mode the car drives fine. when i switch to power mode, the light comes on. car still feels like 210 hp and when i accelerate heavy, the car pulsates and vibrates. when i let off and drive normal, the pulsation goes away.

im thinking its the secondary injectors that may be the problem as i continue to read in the other posts.

I would like to be sure before i invest in them. Also, if it is the injectors, is there anybody you can recommend with a decent price? Im from Canada if that makes a difference. Maybe the local parts shop can order from a major supplier.

sorry, one last thing... any advice or tricks to do an oil change? and is it true the zr1 takes 12 litres?

thanks in advance!