When I was looking at Sinister, there were too many things I couldn't really determine without a wideband O2, dyno, and a scantool capable of logging to a PC.
I'm getting closer now.
I have a wideband O2, my Gtech shows my shifts and where they come with relationships to RPM'*, torque, and HP peaks, and my scantool will record, but not download to a PC.
I MAY have to have a custom chip burned to replace my stock PCM and Jet Chip this year. Car is doing pretty well, but it may require some PCM tweaks and fuel injector changes.
The best thing you can do right now in fairly stock form, is try to get some dyno/gtech data from another L27 with the same gear ratio, and see where your shifts are with relationship to your hp peaks. Tweaking that to optimum may provide quite a kick in the shorts. You may also want to consider firming up your shifts with an adjustable modulator. It'll keep you happy, and your clutches will last longer.
Simple mods like a good CAI or a ported K&N'd airbox you'll feel. Your motor wants to breathe.