A friend of mine did some testing at the dyno on his 01 Cobra.
First pull was with paper filter and snorkel=223rwhp
Second pull was with K&N and snorkel=225rwhp
Final pull was with K&N and no snorkel=223rwhp
Notes: These runs were made at 5300ft, so they are low.
Also 2rwhp is negligable on a dyno, it very well could have been dyno error or heat in the motor, so the results were inconclusive on his car...