when do I know it's time for a tune up?

[m4gician]

Just wanting to get peak efficiency and performance outta the old granny and want to know exactly when it would be time to get the tune up done? I'm going to use irridiums, and add the 3530 but all of that has to wait until I get the SVT exhaust on :s. The reason being the SVT exhaust will go on, resonator comes off, and y-pipe get's optimized, then I do the other mods and well ... tune up how much of a difference will I be looking at (not in whp, but in driveability).

[RawBurt]

Wait, I'm confused... Do you have a 3L or did you not mean to post in this section?

I'm going to use irridiums

I would used the tried and proven Autolite Double Platinums

how much of a difference will I be looking at (not in whp, but in driveability).

You'll probably notice that your car is more responsive, thats about it.

[Big Jim]

Any time after 60,000 miles.

If you do it soon enough, you should not notice any difference in drivability. Cleaning the injectors, throttle body, and chemically cleaning the intake manifold will make a much more noticable improvement.