Hi,

Does the 1990 RR 3.9 have cats in the exhaust anywhere? I can't see anything that looks like one on the Y-pipe...two bulges but they don't look removable

L

Don't think the 1990 has catalysts. Think catalysts came in on 91.

If it has them you can replace them with the Y pipe of a non cat version. Catalysts are expensive £350 + each

Charlotte

Nah, it just has y pipe to one mofo of a silencer. Which is coming out after the MOT

If one removes the cats on a 3.9 V8, the tune resistor must be changed too. The tune resistor tells the ECU if the vehicle has cats or not, so the fuel maps are adapted in consequence. It is usually located on the wiring harness immediately outside the ECU, an ordinary-looking resistor in a piece of clear soft plastic tubing, and it's a simple matter to change it. Non-cat resistors are available as a standard RR spare.

The Lambda sensors must be removed from the system too, just clip off the wires (be sure they are insulated and don't hang around the exhaust).