2001, 4.0, auto trans. Recent upgrades include viper coil mod, Thor intake, 4 hole injectors from k suspension, BBK TB, banks monster exhaust.

So, after doing some poking around on here, it would seem there are several common spots to check for vacuum leaks on these things. After recently diagnosing and fixing a MPG drop (O2 sensors related), I experienced ANOTHER drop. This was after swapping in a BBK throttle body. When replacing the OEM, I noticed the vacuum line (MAP line I believe?) rubber sleeve that mates up to the throttle body is cracked pretty badly. It wasn’t throwing a code or causing issues, so I let it be and just threw a hose clamp on it. Jeep ran like a top, and between the banks monster exhaust, Thor intake, new injectors and BBK TB my mileage was showing a noticeable improvement.

That was a couple weeks ago. I just threw a P0456 code, and saw a huge drop in gas mileage, plus it started running rough at idle. The gas cap is a replacement OEM one from a couple gears ago, so I’m not sure if it’s the culprit. I have a replacement rubber piece for the MAP line being delivered today, so I’m hoping that’s the issue.

Any other suggestions on what to check? From what I’ve read, I need to examine the following:

-Charcoal canister and lines front and rear (need to locate the rear one)
-HVAC lines
-Gas cap
-MAP sensor vacuum line
-Fuel filler neck

Anywhere else I’m missing?