I recently bought a used stock intake manifold because I wanted the injectors out of it. After dissasembling it, I thought I might smooth it out and polish it. I was gonna grind off and weld up the area for the fresh air injection and a few of the vaccuum nipples. After examining it, I realized the EVAP system uses two of the larger nipples on it and the lines tee together underneath it. My questions are: why would it need two if they tee together anyway? and has anyone, that is using the stock ecu, reduced it to only one vaccuum line and not gotten a CEL?

 

Are you sure you're looking at the EVAP system? Those 2 rubber hoses that come from the front near the intake manifold are not T'd under the manifold. They are 2 distinct pathways. If they were actually T'd together, the system would not work. You may be looking at something that has no relation to the EVAP.

 

The tee is metal and the line goes from the tee into a solenoid and then to a capped service valve. The little tag attached to the cap say EVAP service port. Here are some pics of the tee, attached components(the piece of hose between the tee and solenoid is not turned as it would be on the car), and the locations of the vaccuum nipples on the intake(they are circled blue and the visible parts of the tee are circled orange).

 

OK, now I see what you're talking about. I don't know what the reason is for having 2 openings from the manifold unless there is a separate chamber inside that creates a differential. Sorry, can't help ya.

 

The reason for the T is for even dispersion of the evap fumes. Having only one may cause s cylinder imbalance.

 

An imbalance would cause an emissions issue or a performance issue?