If it works and is easy to build it would have been done on a large scale already. There are always reasons why everyone isn't doing these things. They are either exceedingly complex and costly to implement or they are scams. Otherwise, smarter and richer people than us would have it on the open market and it would be no secret.
Just my $.02

85 4Runner 22re, mostly stock. Over 340K miles(SOLD for $4000 7/06)

98 2.7 4cyl 4Runner Bone Stock perfect 200,000 miles (alright, it has a HG and clutch in it's past)