Found these doing a search; although, they aren't all GT Cruiser or SRT specific, they are still a plethora of good, basic turbo tech info.
I recommend starting first w/ the dodgegarage; then thrasher, xmission, allpar, and so on. I'll be reading this stuff til the cows come home.
Thrasher is a group of SAE types who started a side business modifying Buick GN's and have gone on to GM 3800 Supercharged cars; they KNOW there stuff - trust me!!! I used their mods on my '89 Turbo Trans Am years ago.
The dodgegarage I happened upon and found it to have "tons" of turbo tech info.
The remaining sites I found to be informative; although, you'll have to surf them to find tidbits of relevant info here and there.
http://www.thedodgegarage.com/turbo.html
http://www.thedodgegarage.com/turbo_myths.html
http://www.thedodgegarage.com/turbo_fun.html
http://www.thrashercharged.com/chips_htm/gnttype.shtm
http://www.thrashercharged.com/L67_htm/exhaust.shtm
http://www.xmission.com/~dempsey/perform/
Read this part on the link above:
Recipe A - the safe, simple way
Here we go with the safer, 'traditional' method of performance enhancement. I advise you to read the entire recipe before changing anything, just to understand what will be happening. These steps do not need to be performed at the same time; if you must do them at seperate times I suggest doing them in the order listed.
Step 1: the most important change you can make.
If increasing performance is your desire, the first thing you ought to change is the computer.
In fact, if you make only one change to your car this should be it. The Mopar Performance computer increases your maximum boost pressure, plus it eliminates the 'peak boost for only 10 seconds' and 'max boost only after 3000rpm' features. The computers can be purchased through most Chrysler/Dodge dealers for somewhere between $150 and $300 and installation is a simple 5-minute operation. Back when first introduced, the MP computers claimed to drop a full second off the 1/4 mile ET of your car. With the right car and the right driver, this might be possible; in the real world it is safe to expect an ET drop of .5-.7 seconds.
http://allpar.com/forums/index.php?act=SF%26f=18
http://www.allpar.com/mopar/24.html
http://www.allpar.com/neon/neon-srt-4.html
http://www.allpar.com/trouble.html
http://www.relentlessracing.com/
http://www.turbopiping.com/pages/2/index.htm
http://pages.cthome.net/gus/tech.html
http://pages.cthome.net/gus/pictures.html