Car stranded us. Plenty of power but wouldn't start, then hours later would suddenly turn over with no problem. Our mechanic ended up replacing broken/worn radiator return hose, then when it still wouldn't run, mechanic replaced head gasket (small oil leak)and spark plugs. Still kept cutting off, then ended up replacing the ECM which had to be flashed to car. Import dealership said it was still throwing a code, but our mechanic said it wasn't on his machine and pronounced it fixed. Weeks later, now selectively not starting, driving normal then seems like no power, to now not even starting at all. The last drive in it, check engine light came on, code p0420. Catalytic converter? This car has two. Second question? Was it the cat all the time and we got taken? Thanks for ANY help with this.