Crank pulley

Why do you ask?

I hope your not going to replace it with a lightweight crank pulley

If you are i insist on informing you why that is a bad choice.

The stock crank pulley is also a torsional dampener that prevents the engine from disentegrating itself by reducing the vibrations that an engine makes.

You see at a certain hz of vibration (if its intensity is enough) every object will shatter. Your engine will create these shattering vibrations roughly 3 times throughout the rev range and without the torsional dampener the crankshaft will in time prematurely fail.

Interesting...I've had a lightweight crank pulley on my Tacoma for over 100k miles now with no issues.

The Tacoma didnt have an engine that was engineered with a harmonic dampener.

High performance engines with tight tolerances are built with harmonic dampeners because any uneeded vibrations would cause the engine to prematurely fail.

Toyota first started engineering harmonic dampeners with the 2jz engine in the supra and you will not believe how many 2jz engines failed due to replacing the harmonic dampener with a light weight crank pulley.

Read these articles and you will understand what i am talking about
http://www.atiracing.com/products/dampers/damper_dinan.htm?b1b7cb08

http://www.suprasonic.org/public_html/sonictech/tet/dualratedamper.html

Yeah, Yamaha and Toyota did a lot of maximizing with the 2UR-GSE V8. Disturbing the harmonic balance of this engine would only cause trouble.