The 3 cats are there for a reason ( the V6 Cast heads ) need the back pressure that the Pre cats produce I sourced a V6 and a 4x4 mondeo to basically give my V6 a 4x4 Transmission, Couldn't do it due to the rear Pre cat was in the way of the front Diff, Powerstation ( RR and Tuning company near me ) Stated the engine would need a full rebuild if i took the Precats out as the head was to 'weak' to last long with out them... They advised me to source SVT heads, UIM and LIM's as they have stronger Valve seats ?? But at the end of the day. Its your choice.