all the info you need
http://www.andyforrestperformance.co.uk/16307.html
or for the VF series
VF22
This turbo has the highest output potential of all of the IHI VF series turbos and is the best choice for those who are looking for loads of top end power. . The VF22 spools significantly slower than the rest of the IHI models due to the larger P20 exhaust housing and is much less suited for daily driving than some of the other models. Although the largest VF series turbo, the VF22 is not best for those who wish to run more than 1.5 Bar of boost as you'll find pieces of the turbine wheel in your engine Sad
VF23
A great all-around turbo. Like the VF22 it utilizes the largest P20 exhaust housing. This housing is mated with a smaller compressor housing of the of the VF24. This turbo is considered optimal in applications with range from mild to slightly wild. Notr as much top end power of the VF22, but spools up faster.
VF24
This turbo shares its compressor housing with the VF23 however, this housing is mated with a smaller (P18) exhaust side. Great bottom-end power and quick spoolup. A popular turbo for Group N Impreza rally cars.
VF28
This turbo came standard on the STi Version 5. In terms of overall size, it is smaller than the VF22, VF30 and VF34, and about same size as the VF23.
VF29
This Turbo is nearly identical to the VF24, with the same compressor and exhaust housings. However the compressor wheel in the VF29 is has been changed slightly. The changes made to the compressor wheel in this model are generally viewed as improvements, and as such this unit is typically chosen over the VF24.
NEWAGE TURBO'S
VF30
The VF30 is commonly considered the best "kick for your quid" turbo in the IHI VF series line. VF30 features the same exhaust housing as the VF24 but a larger compressor side similar to the VF22. The combination of these two parts results in increased output potential without the lag associated with the VF22. Although it doesn't offer the top end supremacy of the VF22, the VF30 is a great compromise between these unit and the quicker spooling models.
VF34
The VF34 is nearly identical to the VF30, with the same exhaust housing and compressor. However the VF34 goes back to the ball bearing design, and in doing so achieves full boost approximately 500RPM sooner than the comparable VF30. The VF34 is the most recent IHI design and as such costs slightly more than its counterpart. Top end performance and maximum output are identical to the 30.
VF35
VF35 The VF35 has identical internals as the VF30 and it uses divided thrust bearings. However, the exhaust housing is a P15 which means this turbo will have fantastic spool characteristics. Great turbo for WRX/UK cars due to 7K rev limit.
VF36
Roller bearing version of the twin scroll VF37, also has a titanium turbine and shaft for even quicker spool. Same compressor housing as VF30/34, however twin scroll P25 exhaust housing provides slightly better top end output due to reduced exhaust pulse interference. This turbo is good for 400HP and used on JDM STI Spec C from 2003 onwards.
VF37 (thrust bearing)
Enter the age of twin scroll IHI turbos. Same compressor housing as VF30/34, however has a new twin scroll P25 exhaust housing that provides slightly better top end output due to reduced exhaust pulse interference. Twin scroll also provides better spool up for improved low down response over the VF30/34. This turbo is good for 400HP and used on JDM STI from 2003 onwards.
VF38
Twin scroll turbo with titanium turbine and shaft. Smaller compressor housing than VF36/VF37. Fast spool up capabilities but less top end than VF36/37. The spool capabilities of this turbo are demonstrated on the JDM Legacy GT, which reaches peak torque at 2400RPM.
VF39
Single scroll turbo used on USDM STI and latest 2.5L STI released internationally. Smaller than VF30/VF34.
VF42
Exclusive turbo to the S203/S204 models, this features a twin scroll design with a slightly larger compressor than the VF36/37 turbo and different turbine design (more blades). The VF42 is a roller-bearing turbo and is likely of similar size to the VF22 turbo, but with twin scroll exhaust housing for faster spool and better top end.
TD Series turbo
TD04H – as found on 97- UK cars and 96- WRX this is a great little turbo with fast spool up rate (typically 1 Bar @2700rpm). This turbo has been tested to levels in excess of 270lbft and 290-300bhp and is a great little turbo for a road car.
TD05-16G - from the 93-96 WRX and UK cars (can also be converted to front entry to suit 97 onward cars). This turbo was very popular on installations aiming for up to 340bhp but nowadays seems to be left aside for the likes of the VF30/34. This turbo will typically spool up to 1 bar boost by 3000rpm and full boost by 3300rpm . A STRONG BASE TURBO, do not underestimate it.