Scanners used: Solus Pro, Crypton Proscan. No DTC`s stored. Came to me with collapsed front pipe cats and cracked exhaust manifolds, Lambda sensors damaged by flying bits of cat. Repaired manifolds and removed front pipes and underfloor cats. Fitted new front pipes, underfloor cats and sensors, also checked rear silencers for blockage, non found. Sensors fitted in correct orientation. Engine now starts and will idle but as soon as I run it up to 2500 rpm it instantly cuts out and stalls, It will restart but struggles to keep running, will not rev andpops and bangs through the exhaust. If I leave it till next day it will start and idle properly but as soon as it is run up to 2500 rpm the same thing happens. Items checked are: ECT sensor, crank sensor, [shows 200 rpm on scanner when cranking even in missfire mode], coil packs [substituted], ecu for water ingress, emissions when running properly, HC 90 co: 0.07. New spark plugs fitted and all show a nice even grey colour so no leaking injectors, injector duty cycle checked, ignition timing checked via half engine speed sensor, Intake checked for air leaks, Maf sensor checked, Removed exhaust from underfloor cats back, still the same. Problem occurs regardless of engine temp. Ideas or help needed, Regards, Neil.