7A injectors are 210cc. To retard timing, you need to jumper two pins in the Diagnostics box (I don't remember which two), hook up the timing light, start the car, and retard the timing at the distributor by loosening the bolts and turning it counter-clockwise until you get your desired timing. Just to let you know, retarding the timing on the ST is retarded (no pun intended) and it's not even enjoyable or healthy. The turbo will spool-up a lot quicker, but the car will be very lazy. I did it years ago from stock 0 to -5 degrees.
About timing, I've boosted 5 PSI with 89 (or was it 87?) octane fuel many times and the engine has behaved like if it was on 93 octane. More (or less depending on ambient temperature) and the engine starts retarding timing. You can feel it because the car will not pull any stronger than at a lower boost setting, and you can hear the turbo sound different. If the engine needs to retard too much, it'll go in limp mode, with a cool orangey-sweet CEL for your enjoyment. It's oh-so-lovely cruising at 50 MPH while the turbo is spinning its ass off, with snail-slow throttle response to boot.
I've tried to break this engine. I boosted 15 PSI on 93 octane at WOT (MX-6 turbo injectors, which are not enough fuel by the way), and the car would go nowhere, while the turbo sounded like a 747 about to take off.

What am I trying to say? Forget the S-AFC. 15 PSI should be no sweat at 93 octane (if the puny rods don't snap first, but that's not the point here), yet, the engine starts playing with the timing like crazy to save itself. You'll never feel the satisfaction of your car running 100% perfect. Depending on ambient temperature, sometimes it'll feel slower than others, because timing will vary so much. 3 PSI one day will feel fast as heck, and 10 PSI later on the day will feel slower, regardless of what the boost gauge tells you and how loud and fast the turbo is spooling. I recommend getting an EMS that controls timing so the engine will behave more consistently. This is based on my experience, of course, not a blanket statement.
This post has been edited by OOBE: Nov 29, 2007 - 3:16 AM