SR20DE help -- power loss

A friend of mine is having an issue with his mother's SR20DE-engined B15 Sentra SE. Not sure of the exact year but it's a pre-SE-R so it's probably pre-'02, and it's a slushbox car.

The issue is this: There seems to be a serious loss of power, almost like "something is choking the engine out". He at first thought it was a clogged cat, and then an intake restriction of some sort. But the intake and exhaust are both clear. Everything else that is easily inspectable (plugs, filters, etc, other tune-up items) seem normal. Are there any specific issues with this engine that might be causing a power loss like this?

More info: His mom is elderly and she doesn't drive the car that much; mainly short-trip in-city.

No CEL? How is the temperature? When was the last time the timing kit was changed? MAF is a sure possibility. I don't think the engine has any really unusual engineering, so a problem shouldn't be exceedingly hard to pin point.

If you haven't checked yet, I'd put my money on MAF sensor. Check behind it for any leaks. I know on RB20DETs the MAF is right butt up against the intake, and that may be the case with the SR20DE as well.

Check all the vacuum lines and make sure that IACV is working properly. (may get gummed up when not driven often) Check the PCV valve as well.