'03 2.3L DOHC oddities

[riscorpian]

'03 2.3L I4 DOHC here, and I'm having a hard time telling if my engine is screwy or perfectly normal. On the passenger-side, I hear the high-pitched whistle of a typical vacuum leak. I sprayed carb cleaner all around there, but didn't find anything. It's very very faint, and I can't narrow down the exact source. Is it possible that I'm overanalyzing it and this is just normal? Or is there something else worth checking out? Idle seems to hang at around 700–750 RPM and doesn't really feel rough, but something just feels really strange.

It has had a relatively dark history of vacuum leaks in the recent past. About half a year ago, I had the PCV valve and hose replaced since both were shot (this was before I became my own mechanic, so I just took the shop's word for it). A few weeks ago, I encountered the infamous intake manifold cap issue, so that's been JB-welded back in place. Last week, the regulator line fell off, but it wasn't damaged. So I plugged it right back in.

Additionally, I can hear a faint clicking sound that seems to be coming from one of the pulleys (can't tell which one). Is that normal, or should I look into this a bit more? It's only audible with the hood open. And I don't know if the drive belt has ever been replaced. Last time I checked it, it still seemed to be in practically-new condition. No cracks, no slippage, and not even faded in color.

Lastly, I noticed that it takes a few more cranks than usual to start it when the engine is warm. If it's cold (been sitting for a few hours at work or home), or hot (in and out of the store), there's no problem. But if I leave it for 45 minutes or an hour, it takes about 2 seconds to turn over, and it starts rocking semi-violently right before it does. This started happening right after I changed the fuel filter, but I don't see how that could cause it. Again, only when warm. Hot/cold are fine.