Change to your plugs Autolite 764's, and get rid of that 10% pulley. It is harming you more than doing good, because the IAT's are causing the knock sensor to retard the timing. You need to change to a cooler plug, the 764's effectively act like a cooler plug because they don't extend as far into the combustion chamber. If you want to go the next step switch to the Autolite 103 which is effectively 2 ranges colder. There is a FAQ on spark plugs on the SCCoA forums, check there for more data on this subject.
1990 SC AOD 1.7L AR....11.75 @118
441 RWHP 435 RWTQ