I just received my Super Streetbike magazine in the mail (march 2012). They conducted a test of the Takai racing coils on a 2011 Honda CBR 1000. The bike had a dyno baseline of 159.88 hp and 78.71 trq. After installing the coils they had 163.43 hp and 81.68 trq. Not quite the 5 hp they advertise but worth the purchase in my opinion. I was a little shocked over the additional 3 lbs of trq. Overall I think it's a good upgrade for their test bike. I hope i see the same if not more results.
I wonder how good / strict their testing procedure was? Did they do ABA (ie, do dyno runs with stock coils, then the new coils, and then go back to the stock coils)???
If they just did A-B, dynoing with stock coils, then dyno with new coils....
If they're doing a bunch of runs with both, that could be 15 pulls each. So that would be 30 runs total
Over the course of 30 runs, you could see a horsepower difference like that, w/o any changes being made. Changing engine / coolant / oil / fuel temps, change in wear / friction with the tire & chain, etc etc etc
In other words, a 3 or 4 hp difference is small enough to just be testing error.
On the other hand, if they were worth a true, reliable 3 or 4 hp, well thats a potential option for someone to make a bit more power, but only if they have exhausted most of the other options.
Something like that might be worth it to the guy who already has cams as big as he wants to run, a ported head, big bore kit, etc etc...
Anyways. I just dont hear many complaints about the stock ignition systems anymore, at least for naturally aspirated bikes (no turbo, supercharger, nitrous, etc) running most gasoline...