15 psi w/o detonation is good but if no scan tool you are talking about audible knock right? There may be knock you cant hear (not to get you paranoid....)
If you want to run as much boost as you can safely spend the 250 on a scanmaster from ramchargers.com......it's really much safer to know exactly what's going on. A little rich is safer than alot lean regardless....
The wastgate solenoid I would connect because it protects from accidental overboost. If it is as old as the car I would replace it. They are like 35 bucks i think....also the three little black hoses and the Y. When I did mine the Y had a metal restriction which had to be drilled out per recommendation of the place I bought it forom(poston).
Your chip I am not sure, was it burned for those injectors or were both there when you got the car?Eric will get the timing right for you......chip burning has come a long way recently//
Chris