I don't think those are the correct o-rings in the middle section. I replaced 3 sets of injectors in my truck, and all of them were round o-rings, not square o-rings.
Buy an O-ring kit and check that out.... Thats my thoughts
After years of use the o rings form to whatever shape they're placed in. The tubes are flat walled and that's why the o rings get flat on outside edge. I would replace the orings before re installing them or I"d buy new alliants and put them in.