Regarding intake and exhaust mods, it has been proven time and again that on the VQ35 and VQ37 engines that it tends to lean out the A/F ratio. The ECU tends to compensate by pulling ignition timing. However, once dyno tuned properly with just these mods, there are some nice gains to be made without the ECU pulling time, especially at the mid range. Can easily maintain the stock ECU and have a custom tune done if the tuner uses UpRev or ECU Tek.