Any air leaks upstream of the throttle blade only means unfiltered air is entering the engine. It should not have any impact on engine running. The presence, or absence, of the 'stinger' in the air filter housing means nothing, as it does next to nothing at anything other than full throttle running.
It's more likely you have accidentally loosened a connection to a fuel injector, the idle control solenoid, throttle position sensor, or perhaps the air flow sensor. You may want to check all of these connectors.
There is nothing about changing out the air filter that would, in itself, significantly change the running of the engine at idle or low engine speeds. Something else has occurred, and you should carefully retrace your steps of the install to see what else you may have accidentally impacted.
I'm with Steve. If you have changed the air intake nothing should have affected the iddle. I changed mine for exactly the same air intake and muscle cover you have, and the operation was simple and it doesn't inply touching anything else but the air intake filter. I mean, there is no reason you could have damaged anything downstream. And if there is air coming through without passing the filter, it shouldn't affect your iddle.
To me this sounds more like a fuel pressure failure. Any warning light - I mean the check-engine orange one - in your dashboard?
