I ran some tests tonight with a PCV on a WR250R.
I made every effort to keep conditions as consistent as possible. Same bike, same stretch of road in the same direction, same technique, no notable wind, only 40 minutes elapsed from beginning to end of these tests.
Bike is completely stock with all systems in place (AIS, EXUP, etc) - just the PCV. I would roll out, dial up 3rd gear, and at 15mph I would crack the throttle wide open and hold it to the limiter. The data was collected by a 10Hz Driftbox from Racelogic, and the 20-60MPH times were interpolated and extracted by the software.
I know these are terrible numbers for 20-60, I wasn't trying to generate fast numbers, just eliminating as many variables as possible (no shifting).
PCV with ZERO map (stock)
RUN 1 - 7.43
RUN 2 - 7.36
RUN 3 - 7.08 (!!)
Average - 7.29
PCV with stock exhaust, stock airbox map
RUN 1 - 7.18
RUN 2 - 7.15
RUN 3 - 7.29
Average - 7.21
PCV with stock exhaust, open airbox map - held the airbox door open with my leg for these runs
RUN 1 - 6.65
RUN 2 - 6.69
RUN 3 - 6.58
Average - 6.64
My thoughts:
I don't know where that 7.08 came from in the zero map set, but it happened...that brought the average of the zero map pretty close to the average of the stock air/stock exhaust map.
The stock air/stock exhaust map actually pulled a little harder than the open airbox setup way down in the RPM range, but the open airbox came back with a vengeance once the revs built up.
Comparing just the median number, 7.36 to 7.18 to 6.65 shows a nice incremental improvement as you add the map and then open the airbox.
Had the median runs started side by side at 20MPH, at the time the airbox bike hit 60MPH, it would have been 8.45 feet ahead of the stock air/stock exhaust map bike, and 22.89 feet ahead of the zero map bike. (Obviously the stock air/stock exhaust bike would have been 14.44 feet ahead of the zero map bike)...
This goes back to what others have already said...this engine is suffocating. Letting her breathe showed a nice improvement. I don't have an exhaust so as much as I wanted, I couldn't open her up end to end and collect that 4th set of numbers.. :/
FWIW, here's a graph with the three median runs: