Lean Spikes
 

I've had many problems with my 87 turbo II since I began the long and tedious project of restoring the otherwise dead car. Something I've never been able to fix or even find what the source of the problem is, are the lean spikes. At idle the afrs are in the 11's that stays the same at a slow cruise. When under slight acceleration 10in/hg to about 5 in/hg of vacuum it leans way out to afrs of 15/20. If i give it a little more gas up until about 3 psi of boost it runs relatively rich (12 afr). From 3psi until about 5 psi it leans out to 17 afr then back to an 11-12afr from 5-7 psi. It goes lean from 7-10 psi and rich again from 10 psi to 12 psi. The lean spikes aren't random and I know it's not the inaccurate narrow-band air to fuel ratio gauge because I can actually feel a noticeable loss in power when it leans out. I don't want to blow my motor up but I can't find the source of the problem. I've checked the o2 sensor, map sensor, installed new 720cc injectors, walbro 255lph fuel pump, and checked the tps. Any help would be appreciated.

is the fuel pressure regulator hooked to a nipple that sees vacuum AND boost? not all of the nipples do, and its easy to have it hooked to the wrong one (i've done it, and ive seen other people do it too)

The fuel pressure regulator was hooked up per vacuum diagram. It's the stock ecu

not good enough. there are 3 nipples in the back, and they do not all see boost AND vacuum.