For all the gear heads that have a clue, what will the following do for me in terms of performance, if anything at all?

Connecting rod bolts
valve springs
titanium retainers

I see these as the only upgrades provided by just about any aftermarket company, but will I see a change in performance by changing all these?

 

Those are all good things to replace if you are going to increse the redline. Otherwise they won't do much for you.

 

Con Rod bolts: Reduce rotating mass? I've never heard of this as a standalone mod. I guess if they deform less than the stock ones it could have a benefit as far as high-revving...

Valve springs: Stiffer ones will allow you to rev higher b/c valve float won't happen as early, but you'll need some kinda ECU mod to go along with it in order to take advantage of this.

I don't know what the last one refers to, so I'll just wait for JTso to chime in.