any power difference between the two and is a reflash needed changing from the K&n to the buschur cone filter?

just the sound

The Buschur cone filter alone is god for 3 - 4 whp - with the suction tube it makes the same as the HKS RS intake kit - about 9 whp

so no significant change in a/f ratio to need a reflash?

You might run a little lean when using an open source air filter like the cone filter so I would recomend a reflash.

The cone style air filters alter the way the mass air flow sensor reads the air flow through the intake. This causes distinctive distortions from the way the stock air box measures the air flow. A retune is needed to compensate for the cone filter.

To be completely honest if you cherish stock like driveability I think you would be better off picking up a drop in K&N panel filter from Buschur, you kind of have to adapt you driving technique with the other choice, at least I did with my BR pipe and cone filter. Although I did see something the other day about David Buschur redesigning his pipe because of so many reports of poor idling and stalling, I'd give them a ring.