What all do you have done to your 3400? Most 3400's that I see when they are stock/near stock put down about 135-140whp. You must have done a LOT of work on your 3400 if you're figuring you gained 25 crank hp (CAI, headers, and PCM tune should get you about 25 more crank hp).

Also, Chibi is completely right. Do NOT get MSD coils and DO NOT get those junk E3 spark plugs. Those things are a scam and you should avoid them.

Good luck with your persuit of more power. It takes a LOT of work to get any power from these engines, until you go boost.