Hi just wondering if anyone knew if there should be a type of cap or cover that should be on the tube that holds the mixture screw on the xr3i fuel metering unit?
Would it have had one when the car was first made at the factory?

Reason I ask is because there is a high pitched whistle coming from that tube on mine and goes away when I put my thumb on it.
I know these MFI''s such as mine are a bugger for vacuum leaks you see.

Whenever I see photos of other people's engines they never have a cap on but this just seems odd to me.

Anyone??