Ah, ok. I did more research. The motor I was thinking of was from the previous generation of legacies to what you're talking about. The first EJ turbo motor was the EJ20G (often called EJ20T) and was in the 91 turbo legacy we got here in the US. The USDM version did not have a proper intercooler though later models did in japan. It was used in the first STi's until 96. The USDM replacement was the EJ22T, which also had no intercooler. The JDM replacement in the legacy GT after 1993 in various forms was the EJ20H (often called EJ20TT) and did have an intercooler, yes.
If it's from a 96 JDM LGT, wiki tells me it's either an EJ20H if it were an auto or an EJ20R if it were a manual. Either way, you're talking about a motor that would be hard to match up with a USDM ECU. Even if you grab the old JDM ECU, good luck programming it. Some Impreza RS guys can talk to you about how much of a pain in the ass the old ECU's were. Your 03 WRX ECU is difficult to use with anything but 02-05 WRX heads. You might be able to rig up the twin turbos but I don't know how much good it would do you. The LGT had more width under the hood than the Impreza and also had the advantage of higher octane gas, better exhaust, etc so don't be fooled in comparing the EJ20TT to the EJ205 just purely in power output. Two turbos are often < one good turbo (ask any 3000GT or RX7 owner about that).
The more useful part of the EJ20TT would be the block itself without the heads, turbos, etc. Assuming your EJ205 heads are still usable, you could go with a more classic hybrid setup. $700 for a used engine stops looking like that good a deal though as EJ257 shortblocks are not much money NEW and offer a 25% displacement advantage.
bottom line is that motor is FAR from plug and play in your car. Do your homework or it'll cost you way more than you think you're saving. Honestly, I think the only JDM motor worth your time would be an EJ207 (JDM STi 1998-2011+) WITH it's ECU and assuming you have working heads, a hybrid would be the cheapest and most cost effective route.
2015 STi: Still Stock
04 STi, 04 WRX: SOLD
Last edited by mosc; 03-14-2011 at 04:41 PM.