The first intake I had was a K&N FIPK, when I went back to the stock air box I tried to use the K&N tube, it didn't line up. I like the AirAid MIT replacement tube I bought, feels like I picked up a few ponies. It was $115.66 delivered, I bought it from www.macromotive.com which is the cheapest place I found. The cost may seem like alot for a tube but I've seen exhaust systems dynoed in magazine that pick up 10 hp for $350+, if I got 5-7 hp for $115, it's worth the cost to me.
Jim
00 silverado ext cab
5.3L Vortec, 3.73 gears with limited slip, Gibson shorty headers, Dynomax exhaust, Ported oem airbox, K&N filter, Volant intake tube, NGK tr55's, ASP pulleys, Yank 2400 TC, Predator, LT1 electric fans, Cadillac Escalade wheels and 275/60R17 tires.
Best 1/4 mile: 14.76 @ 92.23 with a 2.09 60"