As a someone who daily drives a Trailblazer with the I6 (and being the 06+ with better internals) the concerns about them being thirsty and heavily computer controlled is true. Now much of that is for emissions and keeping a 4L65E alive behind the engine. With stock size tires and 3.42 gears, I turn about 1900 RPM at 70, about 2100 at 75 and it does not hunt for gears in the hills at speed. It seems most I6 TrailBlazers had the 3.42 gears which suck for city MPG.
Its a dead smooth engine that likes to rev and had a very broad torque curve. Most of the wiring is actually very neat and not hard to conceal.
The PCM is mounted on the intake manifold, which is composite so its not really exposed to heat at all. With PCM tuning, a free flowing exhaust and air intake it can make well over 300 horsepower.
A couple things are that due to the wrapper of the TB, they can be hard to change the plugs,the starter is in a really awkward place and the engine has a front sump where the front axle passes through on 4x4/AWD models
