I'm in a similar situation with Trey... I'll be upgrading to Toda 4-2-1 over my JDM ITR 4-1 jet-hotted header. (whew, wordy).

My reasoning is Toda 4-2-1 flows a bit better than JDM ITR 4-1 and it does not hang low like JDM ITR 4-1. I've seen plenty of JDM 4-1 headers banged up and with Toda 4-2-1, you'll bust the oilpan before the header.