man you are dealing with the same situatio i am dealing but my engine is a 2j.I have it down to 184-195 f cruising and 195-204 at idle on traffic. before it was in the 200-225F range. I wired a fan wrong and change the radiator cap from 13psi to 16psi. so you know .I have a friend with an isis rad and the cap took a shit in a month
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My shit still slow
618 whp 492 ft/lbs at 22 psi (Low Boost)on pump gas ,
stock block ,more power coming soon ,stay tuned 
Tuned by Alpha @ Induction Performance