hello. my name is dave. i have been working on my sons car, an 88 na that we converted to a turbo. we used all the stuff you said, (lexus afm, 550inj, afr) to use and we are trying to get it to run richer! i am measuring the voltage at the o2 sensor and it is reading .04 volts which according to my sensor book, is supposed to be around .5 volts to be ideal. i will still be looking at checking into stuff to make it richer. i was hoping not to add some add on computer but what ever it takes i will have to do. i would like it if you could help us, thank you, dave.