| the reson guys go with the shim kit is due to the fact if you run a large hp tune it will ask for alot of fuel and when it doesn't get enough fuel the fuel rail psi drops down and if it drops to far down it will give you a 2k rpm governer so with the shim kit it will allow more fuel thru the stock fuel rail..hope this makes sense
i had to do it on my 05 LLY and haven't had a 2k rpm governer since then..
__________________ James 
05 LLY Chevy LS E/C L/B DRW my older brothers truck now
2006 LBZ GMC SLE C/C S/B,sold the truck to my dad for a business truck
My Truck now,1987 Chevy 2500 350 tweaked,6" SuperLift,350 V8 bored 60 over,Elderbrock headers Cam and Titanium Rockers,750 Twin Pumped Holley Carb and some other goodies.crank dynos over 400HP. | 
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