I noticed you said that your egt's were around 1400-1500 degrees at about 50 MPH?? Thats pretty high for cruising at that low of speed IMO. In 5th gear on the highway, at 80 MPH, my egt's are around 1400-1425 degrees. I suppose at 50 MPH, it will be around 1275-1300. Something just doesnt sound right...i highly doubt its your engine not being broken in...esp after how much you have driven it now. You may want to put the stock injectors back in and run stock idle fuel pressures to see what happens. You could have one or two clogged/dirty/malfunctioning injectors..