well i have a 2000 trailblazer, It's ported, polished, bored .20 using weisco, HPD clutch kit, DG pipe w/silencer, HSP oil injection block off kit, K&N filter charger (with no air box) I run 92 octane, and klotz oil 40:1. My countershaft is a 13 tooth and rear sprocket is 38 tooth. My rear tires are 20x11x10's. My main jet is 210.
top speed is around 50 mph (fast accelorater though, i can beat my buddies highly modified banshee's in their first ,second and 1/2 way through third gears) top spped sucks! I live in missouri, so my altitude is ok. I have lots of other mods to, but not to the motor, like .190 ITP's to shave pounds. any body have any helpfor me? (other than buy a yamaha [img]i/expressions/face-icon-small-wink.gif[/img])

 

i have a 98 trailblazer with a Hypershift clutch kit, Hotseatperformance pipe, Moose handlebars, holeshot skid guards, shockwears, and soon turf tamers and K&N airfilter, i dont know how your gettin such bad topend, my guess is your rear sprocket.. my TB beats my friends Sportsman500 when his speedo is pinned at 60, i have had it by my moms car down a road and the car said 55 - 57, i plan on putting a 13tooth front sprocket so that should take me to about 60. if i were you id play around with gearing, jetting, and get a Different pipe, i would suggest HSP or HPD their websites are www.hotseatperformance.com and www.hpd-inc.com hope that helps... oh yea, i am bored .020 over with a wiseco piston.

 

Ive got a 98TB, with mods listed below.
I had the same prob, heaps of bottom & mid ond topped out at around 54ish,
In my case it turned out to be clutching,
With a few calls to Rick (RCR), I tried different combinations of springs, weights & secondary spring settings,
My last test I was on the road, in front of my brother in his car, he clocked us at 61mph.
I havent lost any more mid power, since the clutch mods.
I have since removed my DG pipe, & run a FMF power core 2,
Seems to have more bottom end than the DG, Same top end though.