[Jake]

None of those 3 articles talk specifically about pulleys or a lightweight pulley's effect. If you are going to post links to support your arguement, please find something that goes along the lines of... "Dont use lightweight pulleys because...".

Have you personally had any experience with the effects of a lightweight pulley on an MX6 engine?

Originally Posted by moebius

*sigh*

Harmonic's In The L Series In-line 6 Cylinder Engines
but realize, they are talking about 6 cylinder engines, which are inherently balanced internally, much like boxer style engines.

For more good information about engine smoothness, and why and which engines are and are not balanced see:
AutoZine Technical School - Engine

for four cylinder engines specifically:
AutoZine Technical School - Engine