Having a hard time getting anyone to do the instal...will be doing it myself on a friends lift. However, talked to one guy I called and he said it would cause big driveability issues. He said the downstream sensors control the fuel trim. Gary at X-metal did install the 02 sims. I thought the upstream sensors do the fuel trim and the downstream do the enviro bit. Should I be worried? :dontknow: 05 RC.