I installed the NAPA 6637 filter in place of my stock system yesterday. I offer the following information for those with more technical interest:
1: By removing just the filter box I preserved the original snorkel and battery box. This continues to feed frontal cool air to the area of the filter (while driving), which sits in the open, crossways, just as KWIK shows.
2: With the original stock installation I measured the temperature in the engine compartment by taping a sensor to the master cylinder just behind the air box.
With the outside temperature at 97 F, at 60 mph on cruise, the engine compartment temperature was 115 F to 130 F depending on the direction (North or South) over a 5 mile course. Remember, the snorkel was feeding outside air to the airbox, not the engine compartment.
3: After the changeover, I repeated the temperature measurements with the sensor taped first the the top of the battery box and then to the master cylinder. With the outside temperature 88 F, at the battery box the temperature was 111 F and at the master cylinder it was 107 F. Remember, the snorkel is now feeding cool air to the area of the filter and the engine compartment.
4: From these measurements I conclude it is not worth the trouble of further trying to enclose the filter to force the temperature down close to the outside air temperature.
5: Before the changeover, completely stock, I measured the boost and EGT up a grade as follows: steady on cruise at 60, boost was 5 psi, temperature 800 F. Pedal to the floor, accelerate to 80. Boost was 17 psi, temperature 1100 F.
6: After the changeover, steady at 60, boost 5 psi (plus a little) temperature 850 F. Pedal to floor, accelerate to 80, boost was 18.5 psi, temperature 1125 F.
7: From these measurements I conclude that the reduced pressure drop accross the filter resulted in the extra 1.5 psi or so boost from the turbo, and I can infer a little better power delivery or maybe a little better fuel economy from the changeover, depending on the driving conditions and weight of my right foot.
8: Remember, there will always be small variations in guage readings due to dc voltage variations. I do believe the boost change is significant.