This is performance related, albeit lame.

The deal is this, I notice my engine response is better with it off.
Not much but noticeable.

I took it off for awhile, then popped it back on.
Months went by and now that it is hot out I took it off and the same thing is happening.

Better response, but...

I notice on decelleration from high speeds, there is a slight vibration whereas when the cover was on it did not exist.

My wife's Sunfire has an Ecotec and never had an engine cover and does not have the slight vibration on decel.

I also feel like the engine braking is more with the engine cover off.
But excelleration like I said is slightly better.

Does anyone else with the engine cover off notice this?

 

haha. no? maybe its a placebo effect. i dont see how you noticed anything from taking maybe 1 pounds of plastic off

 

dude it is a piece of plastic... either your imagining things or there is something else causing that vibration.

 

yea i dobut its really doin nething
imo leave it off who likes plastic all over the engine anyway...

 

its kinda like that noise in the car thats always been there and nothing has been wrong. and then you mod the car. and hear the same noise. but now think something is wrong.

cover on or off...it won't make a difference

 

I figured it had to be more of I am hearing and noticing things because it is dampening sounds and with it off, I can hear it more.

I wonder if the vibration was dampened by the cover?

I did not even think about it when I did it, but now I am on my way to becoming the lightest Cobalt... pfft yeah right

 

its probably because you hear the motor more with it off..... i had a car come in complaining of low power. turned out to be a broken corner of the airbox lid(before the maf) he heard the engine more and thought the car should be moving faster it was a weird complaint/fix but same tye of thing here