Hi everyone sorry if this is in the wrong place but just wondering if can get a bit of advice.i have a turbo uk2000 impreza and it was running just short of 300bhp and 1.3 bar of boost after being remapped with with few mods.i took the car in for service and and a few bits and get my exhaust changed aswell was too loud and was advised to take air filter off and put standard box back on(which the garage did) as it can ruin mafs.my exhaust was swapped from 3inch centre pipe to a 2.5 inch centre pipe to quieten her down a bit.but when i got the car back it was only running 0.8 bar of boost so i put my air filter back on and it went up to 1 bar.my question is could i have lost the other 0.3 bar of boost because of the downsize in the centre pipe? And if so would i be ok to get a manual or electronic boost controller and take it back up to 1.3 that it was running before? As it was remapped to that originally i was wondering if that would be ok to do without causing any damage.i would make sure i didnt take it any further than 1.3 without a remap i case of damage.thanks

I didn't think that changing the centre section 0.5" in dia would've made so much difference as I thought that the 2.5" system didn't restrict until 400hp .

What type of mappable ecu are you running ?

If they disconnected the battery could it have switched to a low boost map ?

Is there any change in spool, does it hit 1 bar any later ?

Thanks for the reply.im not sure on the ecu as i have not had the car long and i bought it as it is but i will have a look shortly.and as far as im aware it doesnt have swithable maps for it to swap to.it seems to still boost at the same time just stops at 1bar instead of 1.3.the only other change which i wouldnt have thought would have made a difference is that i have had my dump valve blocked off

It's difficult to answer why the boost pressure has decreased because it's possible the dump valve might have been leaking giving you false readings of 1.3 bar in the first place.

I would be a bit dubious of upping the boost as the original remap fueling was set up to dump intake air and now that air is still in the system with the dumpvalve blanked .

Maybe check what ecu ,board or software it's running and arrange a map tweek with a mapper that deals with your ecu at local dyno .

Would be cheaper in the long run , as if you get it wrong rebuilds ain't to cheap [emoji6]

I will have a look at the ecu in the morning.it could be that with the bov and getting a false reading but i have noticed a difference aswell i can tell it doesnt seem to have quite as much there when i floor it.but the only difference now from when it went in is the smaller diameter centre pipe so cant figure it out.and a new maf aswell as my other one was knackered :( i just thought that if it was running 1.3 before then i would be ok with a mbc taking it back up to 1.3 but i wasnt sure if that was the case as im new to this game still thanks

someone who knows a bit more about mapping might well disagree, I'm just unsure how much the ecu is capable of adjusting the fueling and timing to keep things running safely .

what year uk turbo is it ?

Hopefully someone else will have a bit of input aswell then.its 2000 year in blue :)