New to this and to Subaru's

I bought a impreza ukturbo 2000 last week for £1200 pound, from a friend of a friend. It has vf28 turbo, 2.5 inch straight through exhaust, an Andy Forest remap and is estimated to be around 300bhp.
The problem, it has been sat still for around 4 month and just been on the roads for the last week or so. When i was driving home after about 15 mile of carefull driving and staying out of boost i opened her up in 3rd gear and when boosting it wasnt smooth but harsh and jerky. Also even when idling when warm if you rev high say 4500rpm then let off the revs the revs drop down and the car stalls, it done this when driving home too.
The lad said this has happened before and is the lamba sensor so today i changed that, still happening, i also put 20 litres of shell V-power fuel in as i assumed the fuel that was in would be poor. (10litres was put in before i drove home but there was fuel sat in the tank as the car had been sat for a while)
My mate said it could be the atmospheric dump valve. Any ideas what it could be before she goes to a garage? Much appreciated.

Dan, welcome aboard the good ship NESF. You have absolutely come to the right place to learn about the car......and lighten your bank balance. Sure one of the techs will be along soon with a likely diagnosis. Hope u get sorted.

If it has been sat that long with fuel in the tank, you should of drained the tank and filled it with fresh fuel. However all them problems lead to an Air Leak or a dirty/knackered idle control valve. Other people will help you on here who have a lot of knowledge about these cars. Iv had similar probs with a previous car.
Welcome to the forum aswel mate, keep coming on and join in the crack.

Would the ICV cause my car to stall after revving it high? when you rev to about 3000rpm the revs drop to below 300rpm and the car is close to stall. it only stalls when the revvs have been higher say 4500rpm, or say enough revs to make the car dump.

I cleaned mine and attached new silicone vacuum hoses around the turbo/solenoid area and put a 0.8 resistor pill in and it was job done. Could be numerous other things but is say ICV with me having similar probs

Welcome to NESF   

welcome aboard fella

also there are no warning lights on the dash, yes the lad before me installed eclipse performance silicone hoses, i will look into the ICV. I'm new to all this so when you say things like 0.8 resistor pill it makes no sense but i learn quickly and i think i'm going to need to with my new car. appreciate the help like lads

Welcome buddy

O shit its got the dreaded parts... Just so you know the additives put in premiere files is v power. Momentum and bps one (can't remember) tend to split away from the fuel after 6 weeks of leaving the pumps. Welcome aboard dan

just some more info for yous, it idles fine its only when the revs begin to drop does it stall. if you are carefull and catch the revs you can stop it stalling.

thanks for the welcomes guys, i hear this the place to be when you enter the world of subaru's. i will get some pics later on for yous lot there are some awesome cars just on this post alone!! you will be seeing alot from me as i have big plans for mine. Its my 4th car, ive drove 30 miles in it maximum and already i love it!! just want her running right. Unfortunatley she wont be on the road properly until july as i am only 20 at the minute but come july i will be 21 with a staggering 4 years no claims! so plenty time to get her sweet as nut. ... with your help ofcourse haha

Hi and welcome to nesf   

Welcome aboard   

Get some new plugs in is the first thing id do   

Welcome aboard mate - you'll get plenty of help and advice on here young man - both technical and as KGT says how to empty your wallet on your Subaru as well   

hi guys thanks for the help, plan is to change fuel filter and the ICV then see where i get will keep yous posted

Just clean ICV first mate. It most likely be because its been stood and shite fuel is in the system.

yeah i will, thats tomorrows job, can you recommend a cleaner ?

Brake cleaner mate.

welcome   

Welcome mate

howdy

Welcome

Hi and welcome . Hope you get problem sorted as stated plenty of good lads on here and mechanics etc

welcome pal