Having a big scoop and only a small air hole for the carb inlet or a smallish round air cleaner opening you may be trapping more air inside the scoop than the engine can use on the top end.
That would mean that you are creating a positive pressure or a Ram Air effect, if you can tune for that you will theoretically, make more power. According to folk more experienced than I, a typical design of pro stock scoop will generate 2 psi @ 200 mph. That is 1/7 or 14% more "potential" power if tuned for. I have no idea how much pressure a usual fwd facing mopar scoop will generate at more moderate (140 mph) speeds, I intend to data log the pressure at the rear of the scoop next season and also reference the fuel pressure regulator to the same. Pretty sure something is happening as we do tend to drop around .4 AFR at the stripe, the caveat is I don't have enough data to prove if this attributable to the scoop or not. My 
'74 Challenger..9.46 @ 145.9 1/4, 6.001 @ 118 1/8 so far. 4023lb !!! # N/A, Marsh performance 655ci, Indy Maxx, T/R, Indy 600-13 X's, Street legal, pump gas, full interior, Cal-Tracs, mufflers, 3:73's and real 10.5 radials.
9.51 @ 142.4 1/4, 6.003 @ 114 1/8 with our old mule KB, 572-13, 580 wedge.
RHD '68 Barracuda Fastback 323ci street/strip. Best ET 13.88 @ 99.03
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