So I drive a 2001 Lexus IS300. It's rated, rather optimistically at 218hp from the manufacturer but since it's an automatic, and because well - they lied, it only has about 168rwhp (even accounting for 15% loss through the drivetrain - that's still nearly 20hp lower than it should be). I freaking love the car . . . the quality, the interior, the looks, the handling, the dealership experience - I just wish it had more power and went faster.
So over the last couple of years I've made it my project car. Last night I installed a funky new hand-made header for it from a company called Mazzuri Super. You can see pictures of the header here: http://www.mazzurisuper.com/shop/html/Products/Headers/45.html
This is a "pulse tuned", equal length design and the theory is that the exhaust gases all end up creating a slight suction helping the incoming air get sucked into the cylinder for the next stroke / cycle - improving efficiency . . . each pipe is optimized for the cylinder it mates too, to create maximum power.
Well - I already had an after market header and y-pipe installed - an Alphawerks header:http://www.superstreetonline.com/plugged/parts/130_0403_alphawerks_is300_header/
This was a basic 'long runner' design with no thought (apparently) given to anything other than using few bends and making the exhaust go straight with little resistance. It was good for about 14rwhp. It also didn't sound very good . . . it could be a bit raspy under wide open throttle and there was a drone (resonance) at certain speeds (unfortunately 65mph). But it was pretty.
After living with it for a year I decided to get the Mazzuri to see if it would:1. Fix the drone (it really wears on you over time)2. Give more, noticeable power on the butt-dyno3. Sound better (nice to have - not a requirement)
I am pleased to report that I met all three objectives. My car has a nice deep, throaty Corvette-like growl now . . . which is impressive given that it's only a 3 liter in-line 6. I also have gobs more torque off the line . . . I can trounce on the gas pedal and if the steering wheel isn't straight I can get the ass-end a little sideways - not bad for an e-shift auto. I don't have any dyno results but given my mods (cold air intake, exhaust cam gear, SAFC, header, exhaust) I should be at ~220rwhp . . . up from 168rwhp stock.
What's great about my setup is that I not only make more power - but I do so more efficiently. Prior to modifying my car when it was stock - I averaged about 17-18mpg in combined driving. Now on my daily commute I am averaging an impressive 21.5-22mpg - and that's with my super aggressive driving style. More power, less gas! Win-win!
My next mod will be more aggressive cams when they come out . . . waiting on a company called Brian Crower to get them done . . . but it's been like a year and many people suspect this to be vaporware. We'll see - but once I get that installed I should get another very nice bump and be able to roll with E36 M3's quite well.