I found this post on WRX tuners. I've copied it over here because so many 818 donors are from this time frame and a lot of this info on older turbos is getting hard to find, at least in one place. Al this data is from 2007. Here's the original thread on WRX Tuners: http://www.wrxtuners.com/forums/f95/...-asking-20013/

Mitsubishi TD04L-13T
(390cfm at 14.7psi, 200-275whp, Bolt-On)
This is the standard equipment turbocharger used on the USDM Subaru Impreza WRX. It can be found on all the current model years from 2002-2007.
Expect to achieve full boost with the proper mods and a quality tune between 2500-3000rpms.
Blouch Upgrade
Deadbolt Upgrade
Forced Performance Upgrade (490cfm at 18.0psi)

IHI VF10
This is the standard equipment turbocharger used on the USDM Legacy 4EAT MY91-94. No other information known at this time.

IHI VF11
This is the standard equipment turbocharger used on the USDM Legacy 5MT MY91-94. No other information known at this time.

IHI VF12
This is the standard equipment turbocharger used on the JDM Legacy RS MY89-93. No other information known at this time.

IHI VF13
This is the standard equipment primary turbocharger used on the JDM Legacy MY93-95. No other information known at this time.

IHI VF14
This is the standard equipment secondary turbocharger used on the JDM Legacy MY93-95. No other information known at this time.

IHI VF18
This is the standard equipment primary turbocharger used on the JDM Legacy MY96. No other information known at this time.

IHI VF19
This is the standard equipment secondary turbocharger used on the JDM Legacy MY96. No other information known at this time.

IHI VF20
This is the standard equipment turbocharger used on the JDM Legacy MY97. No other information known at this time.

IHI VF22
(490cfm at 18.0psi, 250-325whp, Bolt-On)
This is the standard equipment turbocharger used on the JDM V3 Subaru Impreza WRX and optional on the JDM Subaru Impreza WRX STi 22b. Of all the IHI models, the VF22 has the largest potential for peak horsepower, and is capable of supporting the highest boost levels. It is capable of running up to 25 psi. The VF22 is a roller bearing turbo that utilizes the P20 exhaust housing.
Expect to achieve full boost with the proper mods and a quality tune between 3200-3700rpms. 2002-2005 WRX owners will need fuel upgrades for this turbocharger and proper engine management is highly recommended for all vehicles.

IHI VF23
(388cfm at 18psi, 250-325whp, Bolt-On)
This is the standard equipment turbocharger used on the JDM Subaru Impreza WRX STi 22b. The VF23 is a ball bearing turbocharger that utilizes the P20 exhaust housing like the VF22. This housing is mated with the smaller compressor housing of the VF24 for fast response and excellent low and mid-range performance. It does not have the same top end power of the VF22, but spools up slightly quicker.
Expect to achieve full boost with the proper mods and a quality tune between 2800-3300rpms. 2002-2005 WRX owners will need fuel upgrades for this turbocharger and proper engine management is highly recommended for all vehicles.

IHI VF24
(425cfm at 18psi, 250-325whp, Bolt-On)
This is the standard equipment turbocharger used on the JDM V4 Subaru Impreza WRX STi. This turbo shares its compressor housing with the VF23, however, this housing is mated with a smaller (P18) exhaust side. The smaller characteristics of this turbo allow it to provide ample bottom end power and quick spool. This turbo is very popular for Imprezas with automatic transmissions and Group-N rally cars.
Expect to achieve full boost with the proper mods and a quality tune between 2800-3300rpms. 2002-2005 WRX owners will need fuel upgrades for this turbocharger and proper engine management is highly recommended for all vehicles.

IHI VF25
This is the standard equipment primary turbocharger used on the JDM Legacy B4. Utilizes a thrust-bearing design and a P12 exhaust housing. No other information known at this time.

IHI VF26
(400cfm at 18psi)
This is the standard equipment primary turbocharger used on the JDM Legacy B4. Utilizes a divided thrust-bearing design and a B14 exhaust housing. No other information known at this time.

IHI VF27
(420cfm at 18psi)
This is the standard equipment secondary turbocharger used on the JDM Legacy. Utilizes a ball-bearing design and a P18 exhaust housing. No other information known at this time.