I had the same header on my SPI for a while back in 2008. I also had a hard time finding a pipe cap for the egr. I believe the one i got was 5/8" but you have to remember that they make 2 different pipe caps, one thatís 5/8" inside diameter and one that is 5/8" outside diameter. I canít remember which one I used. I got it at home depot you can just buy both and return the one that doesnít work.
SEDAN REVOLUTION #110
SPI Owners Club #2