I bought a 2002 monte carlo that has 26000 actual miles and been sitting for ten years. I am getting multi cylinder misfire. I have changed plugs, wires ,coils, gas in tank and still no help. I found this in back floor board but cant find where it goes it is a 3.4 motor Any ideas?

 

I'm not going to say 100% that is not for a 3400, but I am fairly certain is is not. The 3400 in a 2002 Monte does not have many vacuum lines and with how many times I have been around the 3400, that does not jog anything from memory.