will leaky intake gasket make it idle rough and check engine light come on? on 1997 Chevrolet Venture

1997 Chevy Venture 130,000 miles. Idles rough, Check engine light stays on and Flashes when taking off from a stop .Stops flashing when driving.Defentially have an oil leak. New Cat Converter, New plug wires,plugs .Thinking Intake gaskets leaking and missfiring???? Brought to autozone and just told me a missfire code. Would like to pinpoint or know for sure before i change intake gaskets.Van is for 91 year old Lady. I am just trying to help her.Any Help Very much appreciated! Mechanics shops have done all fore said work and charged her Hefty. Still same problem.........

Asked by for the 1997 Chevrolet Venture
The flashing check engine light indicates a misfire on one or more cylinders, scanner can be set to show this misfire while running and which cyl so have that done. Auto parts store cant do it. Forget about the intake!
Hello Thanks for reply. Where can i buy scanner from? New to technoligy. I am old school .
Can you give me any ideas of what might be causing this Missfire?
Will start tearing into it tonight.
Thanks Chris