secondary fuel filter base

Fuel Temp wires and no you cant disconnect them. Why would you want to in the first place?

 

I'm thinking that you're talking about a C-15 with a single turbo and an engine serial number that starts with MBN.

This wire connector plugs up to a solenoid that allows boost pressure through the filter base to activate the wastegate on the turbocharger. If you disconnect this wire you'll have fault codes and the engine derating due to boost pressure not responding properly.

The thing to do is flash the ECM with a earlier 6NZ or 7CZ file that doesn't have this feature written into the file. Then you may remove the complete electronic wastegate and piping if you'd like. With the 6NZ/7CZ file the wastegate will no longer function at all and boost will only respond to the amount of fuel being introduced into the engine.