The Subaru SVX World Network - Engine 'sticking' at 2k RPM on first start

The first time I start the car for the day (or not started for 8-10 hrs) unless I give it a good 5min+ warm up the engine won't go above 2k RPM and goes through surging and hesitation on acceleration, even with hefty throttle. It changes through gears fine. Engine noise is hard to explain because there really isn't one other than it seeming to strain - its more a 'feel' of it struggling or as if it should sould like its misfiring/backfiring.

The easy answer would be "just let it warm up" but the acceleration doesn't feel right generally. She's sluggish unless I really hit accelerator hard. Fuel consumption is also really poor. About a third less than I've read it should be in specs. I'm getting about 6km/L or 14.11 m/g.

I've only had my girl for a bit over a month but this started this week. Initially she did start pretty hard a few times, but some injector cleaner and octane boost seemed to sort it. Fuel economy has been poor since I've had her, but she's been in and out of shops having filters/fluids changed, trans service & steering reconditioned, so I couldn't really tell until now (no shops for a couple of weeks).

I've read through threads and know the SVX has some cold start issues that seem to be put down to the MAF, O2 sensors or TPS, but I haven't found anything that really matches what mine is doing. She goes in for a major degrease tomorrow (hopefully only rocker cover gaskets) and I'd like to have the mechanics look at it - if anyone has any suggestions about what exactly I should have them look AT!

I ran codes - nothing coms up as current on TCU or Engine ('D' check), TCU memory shows #25 & #31, nothing in engine memory.

Thanks in advance,

Tania.
Oh - I live in the sub-tropics so I don't think temp is an issue and it turns over and starts fine without needing gas.