Running lean

I'm new to the forum and looking for some advice for a '94 GT (170k miles). I had engine codes indicating my engine was running lean (181, 189 if I remember correctly). I replaced the fuel pump with a Walbro 155lph and had the injectors rebuilt and tested. I also replaced the head and intake gaskets, valve springs (TrickFlow), wires (Ford Racing), and cap/rotor (Accel). Now I got a 332 engine code (insufficient EGR flow detected) and the same lean codes plus a few more. The engine had an MSD ignition, BBK 65mm throttle body and speed chip (since removed) on it before I got it. Any ideas?

I changed the O2 sensors about 1 year ago. The injectors are stock, and according to the guy that rebuilt them, they were in good shape before the rebuild. Stock fuel pressure regulator. I did forget to mention that since the minor rebuild, it idles at about 1800 rpm. Sometimes the idle will go back to normal (~900 rpm) or stall. I've check for vacuum leaks but couldn't find any.

When I bought it, it had a 65mm BBK throttle body, K&N filter, MSD 6 ignition and coil, Magnaflow mufflers and a superchip. (I pulled the chip out.) I was making good money at the time and planned on dumping a FRPP long block into it. Well, I got laid off after changing the suspension (FRPP springs, Edelbrock IAS shocks/struts, Energy Suspension bushing kit)about 2 years ago. I've added a Catco H-pipe and replaced the cap/rotor (Accel), wires (FRPP), plugs (Bosch Platinum2), valve springs (Trick Flow), fuel pump and filter (Walbro 155lph), and head/valve cover/intake/egr gaskets (Fel-Pro). I also had the stock 19lb injectors rebuilt.