the gm ign stuff is pretty good so no significant gain there, the exhaust the choke point is the converters but i wouldnt mess with that unless you are going to tune it, i would get a k&n drop in you get value for your money, the cold air intake doesnt do anything more for trucks than the drop in and its about 8-10 times more expensive. then i would set the bfg'* on a 1500 crew cab to about 38-40front and 35-37 rear and measure tread wear alot to see if its wearing properly.
1998 Bonneville SSE
2007 Monte Carlo LT-KYB, Clarion, Polk audio, Kicker
1999 Yukon SLE-KYB, Air lift, Reese dual-cam, Tekonsha
1987 Firebird-355/th400-nothing stock