i need to replace my spark plugs. but with so many out there i am not sure which ones to buy. my engine has some after market modifications(AEM brute force intake, Helix power tower throttle body spacer, JET MAF sensor, and a magna flow Xpipe with true duals). i dont know if i should go with a shorter plug because the air mixture has been altered or stay with factory size, also the motor does not have a distributor cap as such, i believe there is a "coil pack"attached to each plug. can you help me in selecting an appropiate plug??? i do also haul campers 16-28 ft. and snowbobile trailers. im just looking for the best fit for my vehicle...