I forget if Steeda does a timing adjuster for 99 and 01 cobras. But that could net you some 5-10 rwhp depending on how stingy the stock timing curve is from the factory.
I'm with the other. Most with your mods would have 20rwhp less then you.
I could not see your dyno sheet with the link you posted.
It certainly is possible. If the dyno run was done in cold weather, and wasn't corrected to SAE, then 330 RWHP is not out of the realm of possibility. Regardless, dyno numbers shouldn't be compared against dyno numbers from another car/dyno. The dyno is a tuning tool - nothing more.
To answer your question....if full-length or mid-length headers are out due to emissions, then there is not much else you can add (the JBAs are pretty good anyways). I would suggest a chip, custom-tuned on a dyno. Mail order is "ok", but won't make all the gains that a competent tuner can get for you on the dyno with a wideband O2.
Also, if you don't already have them, I highly recommend a set of gears, and get as much weight out of the car as you can.