Have had the proform valve covers for a little bit(1400 miles) now and have just learned that by putting the breather caps on it and keeping the pcv hose that goes from the tb to the valve cover I have interduced a vacuum leak? Is this correct? How much would this affect performance? I have read that you either keep the breathers and delete the hose or keep the hose and plug the holes for the breathers. Which way is best? And what size gromet (and where did you get it) to use on the holes?

 

You created a small vacuum leak, but not because you kept the hose running from the throttle body to the valve cover. That's not a vacuum line.

What you did do is allow air that has not passed through the MAF sensor to reach the combustion chamber via the PCV valve (pulling the air in the breather and through the crankcase, through the PCV valve and into the intake). This is a relatively small air flow, and nothing the long term fuel corrections can't correct for.

 

So should I do anything here or leave it as is......

 

I wouldn't run both the breathers and the line from the TB to the valve cover. Either get rid of the breathers or get rid of the line from the TB to the valve cover.

 

Ok with that beening said where/what size gromets to plug the hole/holes?
Rob

 

Which option are you selecting, and which holes are you plugging? The hose nipple on the TB would need a vacuum cap... just measure the nipple to see what size. If you're trying to plug the holes in the ProForm valve covers, it would seem that you need to measure the holes. I've never seen a ProForm cover.

Or did I miss the point of your question?