I'm currently located in the UK and recently bought a '99 Forester STI EJ20T 5MT. I read online somewhere (can't remember if it was this forum or not.) That the issue I am having which is at about 5K RPM I lose all power and have a misfire could be caused by a bad TGV sensor. I have a check engine light as well. I am just curious if anyone knows if this is the cause, as well as if there is an OBD2 sensor that I can use to scan codes,
thanks.

 

Welcome to the forum.
Just to clear up a few things
If it's a genuine "99" FSTI then the engine will be an EJ205. (EJ20T was never a variant)
TGV valves were only fitted from around model year 2001(but not on the JDM SF foresters)
Despite being fitted with an OBD style connector, the only diagnostics available to use at this time was Subaru's own SSM (Subaru Select Monitor). (OBD2 (JODB( didn't arrive fully for Japanese Domestic Models(JDM) until 2008)
What is OBD2? — Stahlcar Scan Tools
However you should be able to obtain trouble codes using the test (green) and read (black) connectors under the dash near the steering column..............



.............using the info in the attached PDF.

As with all Subaru JDM vehicles the "Model Code" from the VIN plate gives a better means for dating as it includes the Revision letter as UK imports are usually registered here by build date.
For the "SF" models "a 99" could mean either a Revision B or C

 

Thanks Don, Im not a huge Subaru guy more partial to Nissan and Toyota. The SF is running fine it just occasionally gets a check engine and has a misfire at 5k RPM any SSM tools you recommend?

 

you can simply use the on-board diagnostic connectors to read the 'flash codes' and that will at least give you an indication