Hey James let me first welcome you to Powerstroke.org! Glad you're enjoying the site.
I run the Diablo Predator on my '05 and generally leave it in the 65 hp "economy" tune. It's friggin awesome. Actually just about aw.....15 minutes ago I had a Dodge dually for breakfast. It's fairly inexpensive too which was an added bonus. In the 65 tune I can burn tires all the way through first into second. In the 100+hp tune she's just stupid fast and I can't keep the tires from breaking through 3rd. SO - if you're looking for fun and speed that's what the Predator does for mine. As far as exhaust, I've got the MBRP turbo back and I've left the muffler but kept the cat. You'll get a lot of opinions on both chips/tuners and exhaust around here, so search around and you should see one that fits your needs.
Take care!