2003 Occasional, brief stumble on acceleration

[MikeDB]

Just bought it, mostly drug around behind an RV by an older couple. Most likely taken great care of since it has Michelin tires that clearly aren't suffering from out of balance or alignment issues.

Every once in a while, upon acceleration (usually? always?), it will stumble very briefly. Two or three quick "thuds" as though the engine is dying due to lack of fuel and then it will take off like it normally does. I drove it around for half an hour the other day and could not make it stumble even once but near the end of my run, it decided on a new symptom: idle fine but sounded like the engine revved DOWN when the accelerator was pressed (I suspect a power drop but there was no stumble at all). Let off and it went right back to normal. Push the accelerator and the engine slowed again. After completing my turn (during which I didn't touch the accelerator), it went right back to acting normal again.

I'm inclined to think fuel pump or filter is just barely starving the engine. Any other ideas?

Edit: Crap, crap, crap! I can't believe I forgot to mention that it throws two codes: 1457 (evap leak, canister side, easy to verify and fix usually) and 1259 (disparity between oil pressure sensor and VTech oil pressure sensor, usually just dirty?). Neither of these are supposed to affect drivability but they could easily help point out something else.

[CapriRacer]

Check for a vacuum leak. It sounds like it is leaking ever so slightly whenever the manifold vacuum drops low.

[MikeDB]

I had not considered that but it sounds more likely than my pump/filter idea. Is there anywhere that a leak typically shows up on one of these? Short of visually inspecting every hose I come across (and in addition to), can you recommend a method for identifying a vacuum leak that won't set me back a lot of money?

Thanks!