The GLT turbo models (turbos introduced on GLTs in 97) use

a smaller turbo. It builds less boost but does build boost

faster. This is called a Low Pressure Turbo. The High

Pressure Turbos (T5s) obvously build more boost and flow more

air. Note, the torque curves I have seen for LPT and HPT show

the HPT has more torque at all engine speeds (many think the

LPT has more -- it probably just has less turbo lag).

The HPT engine has thicker cylinder walls (and thus displaces 2.3

liters vs. 2.4 for the LPT). The thicker cylinder walls can handle

more heat stress. Along the same lines of handling heat are

changes to the pistons and other engine internals (including

sodium filled valves) on the HPT engine. The HPT also uses oil

cooling for the crank (a stream of oil is sprayed on the crank).

Sometime around the 2000 model oil cooling was introduced on the LPT

(and maybe the base engine, not sure). So, the HPT is basically

beefed-up to produce lots of power while the LPT does not use all

of the same expensive parts; but, the LPT is not as stressed so

it does not need all of the expensive parts.

The 2001 LPT produces 210 lb/ft torque wich compares quite well

to the 222 lb/ft of the 850 high pressure turbo models.