ECU Fiat Punto

Hi all, some help would be appreciated

I have a Fiat and recently the exhaust pipe broke from the middle (near the filter of silencer) I left it running without changing it and then I went abroad for 2 weeks and I left it parked and disconnected the battery (I think causing the ECU to reset) then after 3 days or so, the Engine is running half the speed, jurking and missing (it's working only on two spark plugs)

Could there be a sensor in the silencer that caused the ECU to function at half the power or it's more likely that the ECU is damaged ?

If it's a sensor, Could I disable it and reset the ECU and see if it works?

Pls help

Thanks

the Engine is running half the speed, jurking and
 > missing (it's working only on two spark plugs)
 >


How do you know it's only working on two plugs; if you are sure then maybe
they should be looked at first.

Andy<!-- ~MESSAGE_AFTER~ -->