im building a new engine for my 91. i have a first tpi unit to top it off. im new to tpi so forgive me for my ignorance. ken at first said i can use the factory lines. it looks like both pressure and return come from the front. pressure runs into the pressure regulator in the rear that splits the line and feeds both rails from the rear then the driver side feeds back to the pass side near the front and they exit the return line. what is attached to the line that exits off the rear of the driver rail in the foreground of this pic?

 

That is the "9th injector" , the infamous "cold start injector" that was eliminated by GM sometime in the late 1980s.

 

of course it is. geez i forgot all about the 9th injecto thanks.