My sons N15 Pulsar has a GA15DE engine, from what i have seen they are pretty much the same engine as the GA16DE so i will post this here in the hope of some help. Sorry if it is the wrong spot.

The car is a manual with about 150km on it which we recently bought to teach him to drive in and for the most part runs fine, it accelerates fine and maintains speed fine. However it does a kind of throb or bounce (sorry, cant think of how else to describe it ) when under constant throttle at low to medium revs, either cruising at a constant speed or accelerating. At high revs it is fine, though that could just be the momentum of the engine smoothing things out.

It also sometimes feels like it bunnyhops in 1st gear fairly easily, but that could just be me becoming reacquainted with a smaller engine manual car again (and him abusing the clutch :P ).

I have given the car a good service since we got it which has helped; oil & filter, plugs, fuel filter. Also had to change the CV joint and thermostat, but i doubt they will be related. I was thinking about perhaps trying to clean the MAF, but this one is a little different to the others i have worked on, looks like its embedded in the throttle body. Not too sure how to get at this one, not sure if there is a how to section for that?

Engine mounts seem ok, the engine isn't moving around on them when getting on and off the clutch at a standstill, though i guess that doesn't mean much.

Does anyone have any other thoughts what to try?