I ported the head, built a 2" exhaust system, resulting in improved performance at both low and high RPMs, but wanted a rush to the redline instead of going flat at around 5000rpm. So I modified my intake manifold with a larger plenum and a larger flange to mount the larger throttle body. Sounds good, but the flatness at 5000rpm is worse than before. I think that I either don't have enough fuel or enough valve duration to support the mods intended to give me the top end power band that I want. How do I find out what is lacking? I can't just buy the right parts to get it there. I have to make them myself, or have them custom built, because this is a 1.6 liter Kia Rio engine with a 6500 rpm redline. That's right, I came to you Honda guys because nobody builds Kia to be fun. If it helps you hate me less, my motorcycles have all been fast Hondas. Thanks to all who take time to help others get faster, or get to work!