I had to replace my upper intake manifold gaskets to fix a vacuum leak that was giving me two engine error codes (P0171 Bank 1 lean and P0174 Bank 2 lean). I have a 2000 Ranger with a 4.0L OHV V6 with the plastic upper intake manifold. I was able to diagnose it as a vacuum leak with help from an engine computer scanner, a few other on vehicle checks and help from other forum members (of course!!). A vacuum leak in this location is a common ailment for these engines. Here are the supplies / tools that I used: Fel-Pro plenum gasket kit --Part No: MS90732, $21.99 at O’Reilly Auto Parts Blue shop towels In-lb torque wrench External torx socket set Silicone grease O-ring pick Various wrenches sockets, extensions, etc. Channel lock pliers Flat blade screwdriver Things to remember: -Disconnect the battery. Several electrical connectors will be disconnected and reconnected throughout this procedure. In addition, your computer will need to be reset so it can recalibrate without the vacuum leak. -Don’t force electrical connectors when you disconnect or reconnect them. Most have a catch on them that has to be depressed or slightly pried up to get the connector apart. You don’t want to have to add replacing electrical connectors on your to-do list The next three steps can be performed in any order, but this is the order I did them in. Next, from left to right in the picture below, disconnect the vacuum line to the throttle body, the connector to the throttle position sensor (TPS), the connector to the idle air controller (IAC), the vacuum line from the PCV valve, the accessory vacuum line and then the vacuum line to the brake booster (you will have to use the pliers to squeeze the hose clamp together to remove the hose). Remove the wiring harness plug from the support attached to the intake (blue circle) and remove the wiring harness support (green circle). Remove the plastic cover over the throttle body connection to the throttle and cruise control cables. The throttle cable is shown with the red spring and connector. The cruise control cable is black with the red cap. Next, loosen the hose clamp from the intake air tube to the throttle body and disconnect the tube. The cables attach using a ball and socket type setup (green circle in the pic). Use a flat blade screwdriver to gently pry the cables (socket) off of the throttle body (ball). Remove the cruise control cable from the upper intake (blue circle) and then from the throttle cable. To remove it from the throttle cable, pry it up and then off of the pin on the end of the throttle cable (red circle). Remove the throttle cable from the intake. Route both cables out of the way. I removed the spark plug wires going to cylinders 4-6 (driver’s side) as the wires are threaded through the intake. I disconnected the wire at the spark plug first, then at the coil pack (circled in the photo below) and pulled the spark plug end through the manifold. Remove the four screws that attach the coil pack to the upper intake. Remove the wiring support for the coil pack from the intake (green circle). Go easy on it, I broke mine in the process . Lift off the coil pack and set it aside. I set mine on the passenger side valve cover (refer to the next pic). Remove the six nuts that hold down the upper intake. Lift the upper intake up and off of the six studs attached to the fuel rail / lower intake. At this point any connections you forgot will become obvious J. I set the intake on my work bench upside down to replace the gaskets. I am pointing at one of them with my pocket screwdriver. I used a pick to pull the old ones out. The old gaskets had hardened considerably and were flush with the sealing surface of the upper intake. I can see how this would cause a vacuum leak. The new gaskets were significantly more pliable and you can see that they protrude below the sealing surface. I stuffed shop towels in the intake runners of the lower intake (to keep crud from falling in) and cleaned the sealing surface of the fuel rail / lower intake. I checked the torque on the intake studs using the Ford manual. This is where you need the external Torx sockets and the torque wrench. Remove the shop towels and lower the intake down over the studs. Tighten the nuts in the order shown below. I used the e-Torx socket to hold the stud and a crow’s foot to tighten the nut. From here on reassembly is the reverse of disassembly. I used the silicone grease on the connectors for the spark plug wires as well as the socket where the throttle cable connects to the throttle body. Double check all of your wiring and vacuum hose connections, reconnect the battery and then start ‘er up!!