depends on what your planning to do with the car, cant imagine you'll get much change from a grand for that amount of work so not worth doing if you plan to sell. If you plan to keep it and mechanicly its spot on prob worth it, you could easily pay 2k for the same model and end up with a decent body but mechanical dog.
Breaking it for parts is only a limited market, cos its none turbo engine wont be worth more then a couple of hundred and rest has limited value, may get a better offer as a whole breaker
though they were normaly around £600 for a brand spanker fitted and mapped? seems pretty price for a second hand one
when you add £250 RR time for mapping it your up to £700 anyway. alcatek is only £900 fitted and mapped, for £200 more i'd go alcatek, sack the maf etc etc
have a look at alcatek, if your buggering around with piggy backs or apexi (which is donkeys years old now) then while a tad more expensive a much better option.
If its had a new engine then will explain why its running like a bag of spanners, different engine, different map so i expect its never been setup properly.
Sounds like you need to take it to a specialist and get them to have a look at whats what and sort out any faults it has
Need to take it to a mapper that knows what there doing by the sounds of it, shouldn't be getting boost cut on a mapped car unless they have pushed it too far or has setup issues.
For that sort of power then syvecs is the way to go, standard ecu won't cope, i ran my old hawk at 400 and the standard one struggled at the best of times. Don;t scrimp and risk your engine
Also try scoobyclinic at Chesterfield. Where ever you go may sure they check the pulleys and prob find it needs a tensioner (check the price cos alot of places don't include it so cheap price ends up alot higher. Should he warned when you get a quote anyway)
Clinic got a pro drover to test the new one and biggest issue he fed back was brakes. He littleraly fried them in two laps. Change out the front set up for a decent 6 pot caliper setup (stay clear of ksport) and you'll find a big difference. Rear ones can stay as is, most of the braking on a subaru is front end
Don't bother. Get yours rebuilt. Second hand engines are just that. No way to prove the history or how good it is.
My Type R ran fine when I bought it. 6 months later crank bearings failed. You can never tell what's going on unless it's rebuilt from the crank up.