Hi all after owning two Subaru’s n loved them I decided to buy a jdm 2004 sti Impreza off a good mate of mine n I love it I was just wondering your thoughts fuel to use I use Tesco 99 or v power is this okay to run the jdm on this or do I need it mapping cos been read all kinds of different opinions n abit clueless if any one could help be appreciated 

As far as I've heard the jdm models run on 100ron in japan not sure if if needs altered for uk fuel hooefully someone else will be along ti help you out mate. Stunning car btw

Yeah vpower or tesco 99 are fine mate, thats what most of us run on 👍

Anyone tried jets ultimate?

I use tesco 99 in my JDM sti but got it mapped for it the first day after I registered it

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Just seems to have a flat spot around 3-3.5k my mate changed plugs before I got it does any  one no gap on spark plugs should be 

only way to know is get it on the dyno and see what he AFR's are doing. If there's any doubt there might be an issue don't keep putting it on boost, keep the revs low and get it check out. Alot of faults are not terminal until you load it with boost.

You could check the AFR's with a bluetooth OBD dongle and android app like Torque. You basically do not want it to lean out under power and revs. I am not a mapper but you could look at some of the map graphs on this forum and see what AFR they get compared to yours. But Tidgy is right until you get it checked by someone who knows way more than me drive steady.