Back in 1999/2000 when I ran TFS @ Buicks @ Bristol , I tried to max out each of the stock parts and see how much they "cost" in HP vs. a "bolt on" part. I'd go to the track with both parts, run a few runs with one part, swap in the other part, run a few runs with it and see the difference.
The stock airbox/MAF frees up when you open the bottom, but eventually the neck bolt support will start restricing the flow. the neck mount/nut will show up on the timeslip in the high 11's vs. an LT1 sensor in the neck of a cone K&N on the MAF.
The Intercooler Elbow shows up in the 12's vs a Dutt Neck, but its only .1 seconds/2 mph in the mid 11's. The Exhaust elbow vs. a THDP shows up more in the MPH that it does in the ET .05 sec/1.5 mph average in the high 11's, because the THDP seeps to help more above 5K RPM's.
A 100% stock appearing car that runs 11.2's-11.3's is totally possible (with ported heads/cam of course), As I could run 11.7s thru the stock Elbow/stock neck, but I'd estimate with a THDP and Dutt Neck the car will run easy 10.8's @ 5 mph faster with no other changes. The LT1 Sensor neck airbox should still be fine.