I’m trying get my 92 SC400 to run at its best and fastest, any recommendations for what intake system I should run for the best performance?

 

Hello and welcome to the ClubLexus forums!

This may come as a surprise but... in all honesty? Your factory OEM intake is the best available. If you wish you can run a K&N drop-in filter but the standard Denso paper filter is just fine. The stock intake system well is designed to isolate the incoming cool air from outside (via a little duct underneath the passenger side headlight) from the hot air circulating inside the engine bay.

Some owners have also done a modification to the stock air box called the "BFI Mod" which involves cutting three circular holes in the front of the air box and installing little air trumpets onto those for more open air flow onto the drop-in air filter. And with this BFI Mod it is also highly recommended to design a metal or plastic shield/baffle/isolation from the rest of the hot engine bay air. It's a very well documented modification here on the forums but I am not sure how much it ultimately puts greater air flow into the intake path vs the bone stock system.

*However*... since you're located in California I really would NOT recommend doing the BFI Mod because that is undoubtedly going to give you a visual inspection fail (as "tampering") when your smog test comes up.

My recommendation is to not worry about changing your stock intake, focus on making sure your 1UZ-FE is in good tune with fresh spark plugs, fresh plug wires (Denso), fresh distributor caps and rotors (Denso and Denso), a fresh set of O2 sensors (all Denso) and, unless you have already done this, have your main engine ECU sent out to Tanin Auto Electronix to have its capacitors replaced with brand new ones in the same OEM brand and values that it came with. The ECUs in all SC300's and SC400's generally need new capacitor service at this point if it has never been done before since they can go bad and cause issues. Doing that nips any future ECU issue in the bud.

...

There are many other areas of your SC400 to focus on to radically change how the car feels from stock:

--95-00 LS400 or MKIV TT brake caliper upgrade (or another popular multi-piston caliper solution)
--new front lower control arms (OEM MKIV Supra 93-96 spec)
--new power steering rack bushings (go with polyurethane from Figs Engineering or Daizen)
--Supra MKIV rear swaybar upgrade or a drop in swaybar upgrade (the MKIV style is best but requires MKIV rear subframe mounts) or a rear swaybar from Whiteline or another similar company
--17"-18" wheels and tires with a staggered setup running 265mm-275mm rear tires
--Steering wheel can be swapped to one from a 2001-2005 IS300, Toyota Matrix XRS or Toyota MR2 Spyder for slightly smaller diameter and a much more performance driving oriented feel to hand. This is the same steering wheel style that came on the 1998-2002 MKIV Supra ('98 for U.S. and '98-'02 for JDM). An IS300 2001-2005 airbag center can be used with an SPX adapter cable.
--Expensive but an LSD changes the car in various driving conditions and puts the power down better. Several options. Most probably involve having your 3.92:1 final drive ratio diff rebuilt with the LSD.

This all depends on your driving style and how you want to set up your SC400. There are many ways to enjoy these cars from totally or nearly stock cruisers to very modified purist driver's cars.