spark plug questions please help!!!

i have a 1998 ssei with some puzzling issues,car began to misfire badly about a week ago so i replaced the the icm and all three coil packs, car continued too miss and make a pinging noise on wide open throttle so i replaced the plugs and wires which fixed the problem but car still coughs around 5000 rpms though, i replaced the plugs which were autolite 104s with autolite double platinum 106's which is a higher heat range, is this ok?? or am i risking knock retard??? Any plugs that would be better for my car??

Denso plats or the proper AC oe plats are the best.

I currently have NGK TR-6 (stock # 4177), but also used Autolite 605's in my Ultra with 14.5 psi boost with 160 deg stat (warm weather) and have had no problems with either brand. Be sure to check WOT fuel pressure and all vacuum lines & fittings as well as exhaust back pressure. Click Here (http://www.automotiveforums.com/vbulletin/showpost.php?p=6105600&postcount=5) for my experience with high rpm coughing!

http://img227.imageshack.us/img227/8515/ngk.jpg