400ex Exhaust

[mccart400]

I got a 02 400ex and I am debating on whether to get the slip on or a full exhaust.  I'll have a knn air filter and jets to correct air/fuel flow, but id like some opinion on a slip on or the full.  Im really leaning toward hmf, and I have the money to get a full system but i have heard that its pointless to get the header pipe without a big bore, hotcam, etc. because the stock 400 head pipe is decent.  Just wondering if thats true or if itd be worth it for the whole system.  Please help me out. Thanks