Blue Thunder

So ima order some parts for this new 03 cobra im about o get in a few days i wanna order a pulley for the sc and some idlers my question is when i look at the sight lethalperformance.com @ their billetflow supercharger pulleys they offer liek three different package sall with different prices goin from $99-$250 the difference is that each one says it comes with a couple of pulleys all the way down to one pulley wtf doe sthis mean does it mean that it includes the idlers or do i need to buy the idlers and then just the one pulley or what? I've never dealt with cobras before and im real confused.

Basically the car currently has a magnaflow xpipe a magnaflow catback, baer eradispeed rotors, mgw shifter, mm camber caster plates, Chromed cobra wheels with a wider back wheels with some huge MT meats on em (the street radials), the back fenders are also rolled really well. msd coilpacks. I'm ordering a fluidyne heat exchanger, a JLT cold air kit, an irs brace and some idlers and a 2.81 pulley...my question is is there anything i'm leaving out? I wanna make 500-550HP with some boltons will this do it? if not what else do i need to get to make it get those numbers?

BTW the Cobra i'm getting has 4,000 miles on it and is sonic blue and has probably the cleanest paint ive ever seen. This car is perfect!

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Bullitt Mods:
4.10 's , Magnaflow Catback, Prochamber (OR), BBK Ceramic Lt's, Custom Tune, MGW Short Throw, SLP Line Lok, MM LCA's, MM XL SFC's, MRT CAI, Steeda UDP'S, Tokicko Illuminas, Steeda Sport Springs, MM CC Plates, X2 Balljoint, Bumpsteer Kit, MSD Coilpacks, Eaton LSD, 31 Mosers, Spec stage 2 clutch, Spec steel flywheel, M/T DR's.
Cervini's RA Hood, 04 Cobra F. Bumper, 18" Bullitt Wheels, 20% Tint, HID Kit, Smoked Headlights, Painted interior trim(DHG), Seq. Tailights, Billett Stuff.