This has been mentioned before but swapping out the rear end for a 2.82 makes a pretty good improvement in the feel of things off the line, considering the car has 1st gear start alrerady. I know that Feathercarbon has a large volume airbox that was made for Run.exe's 500e, and it's half the price of the Renntech model. Shouldn't be too hard to get it for the 400e, considering this guy's a custom fabricator. I'm not real sure about the headers, I think they are already pretty good and custom stuff would be prohibitively expensive (as far as hp/$$). The exhaust I'm not too sure about but I have heard about the ol' TimeValve Y-pipe thing instead of the center resonator. From what I have read, you should be able to get one made by an exhaust shop for about the same or less than TimeValve. I haven't priced them out lately, so don't quote me on that. If you SERIOUSLY want to get more ponies though, you are going to have to go into the engine, and that means $$$$. I think if you tastefully modify a 400e as mentioned above, you should have a great time and not have too much tied up in it. Better even, it'll be a "super sleeper" due to the fact that it doesn't have the 500e's fenders!! It looks just like a 300e!! Shoot, go for it!! I am seriously considering that or bringing over a "euro spec" 500e from Germany when I PCS from here. They are suprisingly affordable here, but converting them to US spec can be expensive. I just want one because it has manual AC controls available and it's different than the US spec model. Prolly more for bragging rights, really, but there's nothing like saying "yup, it's european spec".