I don't want any "tl;dr", so here's the short:
When I shift and let out the clutch, then give it throttle immediately after, my car will hold the rpms for about one second or so, then accelerate. It almost seems like it didn't grab the gear, and then all of a sudden it's good to go. Power delivery also is not especially smooth, meaning when I hold a constant throttle, it feels akin to a gear in the transmission that has a few sheared teeth (but it is like this in every gear).
Also, when I do a cold start and continuing on until the car warms up, the rpms waver down a few hundred rpm, and then back up again, in what seems like a distinct pattern. It's similar to a vacuum leak, but the "up-down" intervals are more spaced out. Once it has warmed up enough, it stops.
I was told that the latter issue was the IAC, which controls the choke in order to properly warm up the car. This makes sense and hopefully will either totally disappear or get better after I clean the throttle body and the sensor.
While the former issue feels like a clutch issue, I have a strong feeling it isn't because it doesn't slip when going uphill, or when I am full throttling it and hit a rut in the road, and I would think that the issue itself would involve not a lag in the rpms, but a rise in the rpms and a lack of movement. A local mechanic thinks it's a clogged fuel filter, and told me to clean the injectors and throttle body, run a tank of gas through it, and then change the filter. He says that the lag is from the system building up enough pressure to where it gives in and operates normally again (not his exact words, but you get the point).
Do both of these diagnosis make sense, as well as the attack plans? I think I'm gunna hit it with some fuel injector cleaner and clean the TB/IAC tomorrow, but I want to know if the fuel delivery system is even a probable cause of my two issues.