i have a turbo 2000 MY 2000 with a full mongoose decat system.
on my way to work yesterday i would floor it in third forth or fifth and it would boost then hesitate then boost then hesitate all the way to the rev limiter. i took it back to subaru and they had a look at it and said that it was overboosting due to putting the exhaust down pipe on. they replaced a copper restrictor in the boost pipe to stop this and it worked but now it feels slower and isnt anywhere near as peaky. they will put the original restrictor back in for me but they said that it will just happen again. sorry to be so long winded. i need help. has anyone had this and if so what can i do HELP

 

Sounds like they simply replaced the restrictor with one with a larger bore. You could find out what the bore of your old one was, what the replacement is, and get them to redrill the bore somewhere in between.

Or, get them to refit the old one, and clean the wastegate solenoid (which should have been their first port of call). It's easy enough to do, but if you need to remind them, plug the green connectors together beneath the steering column, turn the key to ignition (but don't start engine) then remove one (or both) of the hoses connected to the solenoid, and spray brake cleaner inside everything.

Alternatively, you could fit a manual boost controller such as GBE or Dawes, which doesn't use the wastegate solenoid or hose with the restrictor in...

 

Are you sure it is overboosting? Overboosting feels like you have just hit a brick wall and all power is lost momentarily.

As above really though

 

it was subaru that told me it was over boosting due to the exhaust downpipe being changed. they said the only way they could fix the on and off power thing is to change this thing in the boost pipe which is what they did and now it doesnt feel quite as quick as it was due to it now running less boost

 

This sounds right im afraid! The downpipe lets the turbo spin up freely, meaning overboost with the standard restrictor. The ECU sees the overboost via the MAP sensor and cuts the fuel cut, a fuel cut defender would cure this but BE CAREFUL as no extra fuel will be added to match the boost.

Gareth.

 

so what can i do then. how can i run higher boost if this keeps happening. alot of other people are running more boost and still not having a problem

 

The only reason changing the downpipe would lead to fuel cut, is if the boost was being controlled manually, and had been raised to a point just below fuel cut. The decat downpipe would then allow an extra 1 or 2 psi of boost pressure, even though the manual boost controller hadn't been touched, which would take the pressure above the fuel cut limit.

If you haven't got a manual boost controller, and are still using the stock boost control, there's no way decatting the downpipe would take you from stock boost pressure level to fuel cut boost pressure level. Besides, from what you've described, you're not hitting fuel cut anyway. There's a big difference between hesitation and fuel cut, believe me.

As I posted above, your options are:-

1. Put the standard restrictor back in the compressor-to-wastegate-actuator hose and clean the wastegate solenoid and associated hoses (including the hose with the restrictor in). And check your oil level is halfway between min and max.

or

2. Replace the compressor-to-wastegate-actuator hose with a manual boost controller, such as GBE or Dawes, plug the hose to the wastegate solenoid with a small bolt, and set the boost pressure to 11-12psi.

If having done either (or both) of these, you still have the problem, next bit to check on the list is your MAF sensor...

 

cheers the judge. you have got a very good point there. im going back to the dealer next week and im going to get this sorted. its pissing me off now. ill get them to put it back to how it was and try it at that. if there is still a problem i will do the cleaning and stuff process and see how i get on. thanks,
dan r