I have a 2002 Version 8 WRX.
I first replaced the TD04HL to a TD05-16G - it wasn't a straight swap. The car was also retuned and it made a lazy 175kw. Lazy. It was not a great experience. When on boost, it felt OK. Off boost, it sucked. Avoid.
I replaced the TD05 with a VF30, retuned, 196kw - a WAY more responsive car. I'm so happy with it.
I've also upgraded from the WRX Blue injectors to STi Pink injectors, a STI manifold, that does not have the TGV valves, STi intercooler and a decatted factoy downpipe.
I believe I'm getting limited by the flow of the WRX heads, but I'm not chasing power
Also - I avg 11l per 100k daily driving and about 9.8l per 100k on the open road.