To protect and serve the People of California.
Hey it works so well for gun shows.

California: Police Raid Car Enthusiast Gathering, Generate Revenue:

"If you're not into street racing, why would you need that?" Riverside Police Traffic Sergeant Skip Showalter asked an enthusiast during a similar crackdown last year. "Why would you want more power going to your car?"

Only cops should get modified engines. 

Why would you ever need more than ten rounds in a pistol?

Um, they charged a group of car enthusiasts with street racing while parked?
Warrantless detention, search and interrogation?
Parking lots designated a racing venue?
Looks like the CHPs are just out to target victims to raise more tax revenue.  Plus it's a minority of the population with a hobby not understood by the average person beyond what they see in the movies. 

My dad has a lot of buddies that grew up building hot rods as hobbies.  Some go for traditional stock parts or looks.  Some love to soup up the engines and make a rod like the fast cars they knew as kids.  A lot of the cost goes into chrome parts and high dollar paint jobs, with flames and pinstripes.  They get together at show and shines most weekends.  They may actually drive their beloved autos to the show or the dinner or where ever the club meets.  None of them would subject their cars to the rigors of street racing.  they might get a chip in the paint. 

the look, the sounds, the stats on the power plants, history, and nostalgia drive these guys.  Street racing?  Most people with the money to spend on tricking out their cars also have the maturity and brains to stay away from it. 

if they want to race go to the drag strip, but don't paint the car with a $10,000 paint job first.