Missfire between 3 6 thousand rpm

[sonicS]

hello poeple i new here, jus wondering if u could help me out, i own a 86 2.3 cozzy, it missfires at 3 -6 thousand rpm full throttle, co is set at 1.00 peercent, but when i reduce the co to about 85 its fine, ive gt this feelin its the fuel pressure regulator. Could any one help me ...