I have a second generation Vishnu PROceed with wiring harnesses for sale for $350. I purchased it in march of 2007 for around $1500. I talked to Herman at Vishnu Tuning and he told me that it will boost WHP by roughly 40-45 hp and torque by 60-70 lb ft. Install took me about 1.5 hours and it never tripped a check engine light during my 335i's 3 year lease.
Here is the video of the install vishnu's web site: