1999 Cherokee 4.0 Auto I have been trying to track down a loss of fuel mileage, and a slightly rough idle. I have replaced the coolant temp sensor, plugs wires cap and rotor, cleaned all grounds, replaced both 02 sensors. Yes I have the fuel pump that doesnt hold pressure, but still holds 49, while its running. I purchased a TPS, and it ran like crap, so I took it back and put the old one on. After replacing the 02 sensors I have been getting these codes; 132,135,141,138. I have checked all 02 wires, they are in good condition. My biggest problem and the only time I get the intermittent codes is when the 4.0 starts warms up for say 4-5 minutes it will suck the rpms and engine vacuum up and down up and down. I currently have a tank full of gas and lucas FI cleaner in it. When the problem begins to occur, my vacuum is reduced to like 10 and she starts sucking alot of air. I have cleaned the MAP port, The IAC and the manifold temp sensors. The vacuum slowly reducing to 10 made me think the cat is the problem, or a clogged muffler. The vacuum reads around 16 average on idle. Before I start replacing the big parts I thought I'd see if yall could help with this tricky lil problem. OOO 1 other thing when I replaced the TPS I went for a drive and the darn thing quit shifting, had to drive home in first gear! Any help would be great. Thanks