The S&S headers are the only ones I know of for our cars ( thanks to JBrady ) They're $599 plus shipping and you'll need a few gaskets ( exhaust manifold gaskets and header to catalytic converter gaskets ) and also be able to lengthen the O2 sensors ( can be spliced or possibly buying a passenger side for the driver side application and then splicing just the passenger side ). The install is relatively involved but can be done by one person with the right tools and patience ( I know because I did the install myself ). There are some good instructions on the DIY - see BA_GS400 install write-up for good tips. Expect to pay $500 or more for the install unless you know someone. It's definitely worth it IMO.

The 3.76 Install is a direct replacement of the whole pumpkin - not too bad at all for DIY. Expect to pay about $200-$275 for this install. You'll also need some synthetic differential fluid like Mobil One, Amsoil, Red Line or Royal Purple.

S&S Headers: http://www.headermania.com/mm5/merch...y_Code=LEXUSLS

Good luck and happy modding