I have a 2003 Z71 LT Extended Cab 5.3. Starting out @ 285 hp, I have added a K&N, Preditor programmer, a 2003 SS Silverado Exhaust (My OE Y-pipe was removed and true duals ran into the SS muffler), and am about to add Flex-a-Lite fans.
With this little bit of tweaking, what kind of HP increase would you guys guess I have achieved if any?

 

I would guess at least 1hp per every dollar spent, if you use the decals.

Actually-maybe 30 ponies.

 

$1 = 1hp.......... gm screwed me out of about 25,000 horsepower!!

 

I am guessing maybe 5hp-10. the pre4dator is really the only thing. the exhaust should be changed to something more free flowing. K&N doesnt do much. So replace that big *** SS muffler with something like two magnaflows or flowmaster or something. the put in the cold air intake and get a nelson tune and maybe a stall.

 

Get a set of mid- or long-tube headers, these usually show around 15 horsepower/torque to the wheels and you can really tell the difference with them.

If your gonna do the fans, get an ASP crank pulley and put it on at the same time. I did this and gained 16 horsepower on the dyno. I could feel more response all over the powerband, especially down low.