'95 Altima exterior windshield vent trim removal?

Trying to remove the vent plastic abutting the windshield. I removed the wipers and reached for a metric hex key for the apparently hex screws. None fit. None of my torx drivers fit. I
then tried a narrow screwdriver and the screw tops spin. Are these some kind of pop pin?
The car is often parked under an oak. Leaves and acorns commonly litter the vent top.
Thanks for any helpful advice.
Bill
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Turns out these are pop pins. Some broke from age. There's a single screw in the center. The front edge rubber is also held in with pop pins. The screens were somewhat clogged but not completely. Looking inside I see the air in there goes down the sides of the fenders at the hinges. Below the bottom door hinges there is often an accumulation of leaves, acorns and pine needles.
I was looking for the air intake to the interior. I've had air conditioning woes for years. I had the system evacuated and recharged but the same failure occurs. Air runs fine for a while then stops but will restart after some time - this in very hot weather but works well in moderate heat. I thought I'd give the interior air intake a look before doing anything more serious. Couldn't find it. A possible cause of this air conditioning failure might be overheating if overheating could be caused by the compressor having been changed for one not modified for current freon after collision repair work by the previous owner.
Suggestions?
Bill
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So, the vents had packed, dried leaf matter blocking maybe 50% of the vents surface area. With the vent panel out it was relatively easy to free the stuff with a small screwdriver. I suspect the air flow wasn't terribly effected given the chamber opens to the door hinge areas. It was all back together today and I was out shopping. I can't explain how cleaning the vents could have caused what subsequently happened.
Years ago I started using the cruise control whenever possible while a leg injury healed and continue to use cruise control often. Today I brought the car up to 55 mph and set the cruise control. I decided to check out the interior air flow. It never seemed strong as it should be and today it was about the same. I toggled the air source from exterior to interior while registering the air flow. It was around that time I noticed I was up to 65 mph. It was somewhat downhill but still, I wondered if I could have inadvertently set it 10 mph high. I hit the center cruise button, the green cruise control light went out but the speed continued to climb (WTF?). I was in the slow lane so I carefully turned off the ignition and rolled to the side of the road. I started the engine in park and it started easily but then directly went to 7000 RPM so I killed it again. I popped the hood and looked. The cables were slack. Not thinking clearly I thought the throttle flapper might have come free and was allowing full flow of air and mixture so I started ripping apart the intake. Not far into it I realized it was probably the vacuum. I put everything back together, pulled the vacuum hose off the cruise control and stuck a phillips head screwdriver in the hose, started the engine and it was fine. I shut it down, replaced the vacuum hose and started it again and again still it was okay. I continued on my way.
I still don't see how working on the vents could have effected the cruise control. I suppose some foreign matter got into the works but how? Possibly some vacuum hose under the dash is undone and sucked up debris? But the hose would be in the interior and not an airway that might get air from wherever the air intake takes its air, right? And, where is that anyway? Looking into the chamber with a flashlight while the vent panel was off didn't reveal anything.
Perplexed.
Bill
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