I have a 98 GS Eclipse with a Hahn 2 kit with a FMIC. I also currently have a Apexi AFC and lately being having problems.

When I am idling the pressure on the AFC drops from its normal 450-480 to about 300-350 and my car seriously starts jerking and pushing out pure black exhaust out my Thermal Research Exhaust. It sometimes gets so low to 100 and either stalls on me or all of a sudden jump back up to 450 on the pressure. Also now my car is eating gas like none other. Now I have no clue what this problem is and everytime this happens my Check Engine Light comes back on. The code for the problem is P0455. I know what the code is, it has to deal with the EVAP system. Now also my windshield washers is now barely shooting the washer fluid out. It doesn't even make it to the windshield and also was wondering if this could all tie together.

Now I was wondering if I could have a vaccum leak, if so then where should I look for it. If not, then what do you suggest I should do?

Make sure you have it set to sensor 7 in and 7 out. If it's set to that then you have a vacuum leak or (unlikely) a bad map sensor.

Where do I need to check for the vaccum leak?