I have '04 jeep laredo. 47,000 miles,its been stalling,knocking. What could be problem?

I have had fuel injector changed,and I am using higher octane fuel. It stalls/knocks after engine has been warmed up. Diagnostic came up no error codes,but I still have problem.I have '04 jeep laredo. 47,000 miles,its been stalling,knocking. What could be problem?get the lower grade gas if your car is not specifically made for the higher octane fuel. this could be bad because it could have messed with your catalytic converter which can back up exhaust into the engine, and can be pretty costly to repair being that is has precious metals in it.
I have '04 jeep laredo. 47,000 miles,its been stalling,knocking. What could be problem?
You should never need high octane fuel, unless the car requires it or has a problem. Have the diagnostic guy check fuel pressure/volume. Fuel pressure is higher when the engine is cold, or at least, the engine is getting more fuel. If a fuel pump is the problem (not uncommon), hang on to your hat! Expect to pay in the range of $600-$800!