The static test is merely a simple test to get close to the desired A/F ratio to get you started. Most customers having trouble with the static test usually don't fully understand the procedure and what to look for; one common error is performing the test with incorrect cylinder pressures, which is easily corrected. However, there are certain vehicles (namely turbo and supercharged cars) that may not respond as expected, but that is not a problem at all, it just means that a road test is required.
The road test is the best and ONLY TRUE TEST for determining whether the car is performing well on the nitrous and this is verified by inspecting EACH and EVERY spark plug after a nitrous run. This will tell you whether the A/F ratio is correct and no trouble is occurring in any cylinders; it also provides N/F ratio your engine requires and that will be the one you would use on each and every power level adjustment.
The A/F gauge only takes the average of all cylinders (unless each cylinder has its own, but it's EXPENSIVE), therefore you would not be getting the full story on the condition of the engine on the nitrous system. Your application doesn't require such a gauge, unless you intend to make adjustments constantly to your engine. There are many many WoN users with street cars like yours without A/F meters.
If you have any questions while performing your test, just post up here and we'll set you straight.