Lots of variables when it comes to tuning. First things first, before you start tuning, make sure everything is as it should be. I have chased my tail on a couple of occasions trying to sort out problems to find out that something basic was off. Check here:
Quick Reference Page For the '86/'87 Turbo Regals and '89 Turbo T/A to make sure everything is as it should be. Also consider the spring cleaning guide as well.
Before you start cranking the boost up, make sure you have enough fuel. I take the fuel pressure gauge I got from caspers and stick it under my winshield wiper to make sure the fuel rises on a 1:1 ratio with the boost. If you have your base FP set at 40psi with the line on, it should read at 55psi at 15 lbs of boost.
CEI - Casper's Electronics, Inc. If you dont get a 1:1 ratio, you need to upgrade/repair your fuel system.
Once that is done you need a way to monitor what is going on with your car. Most importantly, to me anyways, is monitoring knock. I try to tune for no knock. Knock kills head gaskets and can damage your crank, bearings and pistons. I would rather give up a little bit of speed than drive over the crankshaft anyday.
If you are using a scanmaster, keep an eye on your O2 millivolts at the top of 3rd gear. All cars are different, some might knock at 760, some at 730??? A wide band O2 sensor will give you a more accurate reading I believe. From what I have read and done, 11.0 under boost is safe. Depends on how hard you want to push your car. Lean is mean, but dont get greedy. Knock under lots of boost can have devastating consequences. With the new 6.0 chip from Tubotweak, you can set what you want your WOT Air/Fuel ratio to be and the chip does all of the work for you.
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How you actually do the tuning depends on what you have to tune with. For most of using still using the ECM and an aftermarket chip, you can change your timing and fuel. Add timing = more power, but again watch out for knock. Reduce fuel = more power making it more lean, but again watch out for knock.
I also run a LS1 MAF, using the translator from Full Throttle:
FULL THROTTLE SPEED - Items Page which also allows you to change your fuel and timing, but not as much as you can with the chip. I prefer to make changes in the chip rather than altering my static fuel pressure at the rail or with the MAF translator. The changes I make in the translator are much more subtle than the changes in the chip, so I guess you could say they are for more fine tuning.
I use the Powerlogger from Full Throttle as well to datalog. With my boost gauge, knock sensor and scanmaster it is sensory overload for me. I watch what my boost gauge is doing and watch out for the lights from the knock gauge while trying to keep the car on the road or in the groove. Some even use an audible knock sensor. With the powerlogger I can review what happened on that particular run afterwards. I dont recall everything it monitors, but it is more than enough to get your car to get your car is a great state of tune.
Some can get there cars to 20# of boost on 93 octane. I have pushed my car to over 30psi on C16 and Q16. Alky will be my next project so I can keep my car at 25psi all the time. I hope this helps and if you have any specific questions just ask.