I have a 2002 Chevy s10. This is the LS 2.2L and my 5th S10 but my first 4cyl. I am having issues but it gets alot worse when I turn the ac on. It bogs and stumbles and doesn't accelerate like it should. I just bought this truck so I was going through the normal tune up stuff. Spark plugs, wires, coils and all that. I have great spark. So I ran codes and had O2 code pop up so I changed that and the code is gone. Then I got a 0718 code for flex fuel sensor. So I changed that and the code is gone. But no change. So then I found a way to check the flow of the catylic converter and it showed blockage. So I took it off and beat the guts out of it and put it back up. Truck runs a little better but still the same problems. I changed the fuel filter just incase it was a little clogged (it was) but still no improvement. I'm lost so I started tracking vacuum and found several lines cracked and leaking. So I replaced them with new vacuum hose. But nothing changes. So I found this vacuum line coming off of the intake that someone has capped. (see pics) when I take the cap off it completely changes the truck but doesn't fix the problem. So I think this might be my issue. I'm not getting any codes now. Can anyone shed some light on this please. I'm lost. Thanks in advance.