My truck has been making a slight whistling noise occasionally on acceleration and I can't seem to pin point the source. It does not sound like a belt or bearing. I was looking around under the hood today and it seems like I have vacuum at the oil dipstick. I don't ever remember it before. Anyone experienced this before? could this be the source of my noise?

 

I once had a slight whistle from a vac leak on my truck and it turned out to to be a blown intake gasket. When you pull out the dipstick does the trucks idle change?

 

Its from the Nitrous plate. We installed 3 nitrous kits on 3 different trucks and they all did that. 2 kits were Nitrous Outlet and the other was a Harris Speedworks. 2 of the trucks just put a breather where the dipstick goes and the "whistle" went away.

 

How would the plate cause a whistle? I know it's sealing to the throttle body correctly.

 

I have no clue but as soon as we took one off it went away

 

Crankcase vacuum is normal. Remove the oil cap when it is running, and see if the whistling goes away. I wouldn't leave it off for long though.

 

The whistle is only noticeable under load, And is somewhat intermittent.