Sorry for the non ford question!
Ive asked the question on a subaru forum, but My general thinking is that they dont have the vast members and knowledge that we have on here, so here it goes; The car in question is a 2002 impreza WRX,(ecu controlled boost)
After putting the cat back on my car it is running less boost, understandably there will be a small restriction now in the exhaust, but IMO this should not decrease the boost. As i see it the ECU will want to achieve target bost of 19 psi (as before) And so should bled off enough air unril this boost is reached, regardless of backpressure. As a test i bypassed the factory boost controller and used a bleed valve, and yes the car can pysicaly run 19 psi in this manner. So my next train of thought was that i may need to "help" the factory bleed valve as it prehaps cant flow enough now, so i installed a restricor from the compressor housing, no change.
This leads me to the conclusion that somehow the ecu thinks it is reaching target boost, so i can only assume that the ecu does a calculation through the air mass meter? Or is there a seperate map sensor for this? thanks in advance.

 

Do you have the Bosch air flow mater mate?

 

is the restrictor pill still in the pipe work to the boost solenoid ?

 

its pipes as follows; pipe from compressor to "T" pipe out of "T" to wastegate. Third barb on "T" has pipe to solenoid valve, with a plastic "joiner" in between, is this the pill you speak of?

 

no idea

 

look down the end of the pipe work and in one of the pipes at the solenoid end there is a tiny pill (ball bearing looking) with the center drilled out,,,,sounds like its missing or you need another pill with a diffrent size hole,,,,if your running a boost controler then this does the job of the pill anyway,,,the smaller the hole in the pill the more boost you will run,,,so if its missing you will be running low boost

 

surley if its at the solenoid end you will need a bigger hole for more boost? as the more you bleed off the more boost you will make? Ill have a closer look later, its just strangethat it made 19psi before no problem at all, and now is making 14-15psi, the general concensus on the subaru forum is that it is now outwith the mapped duty cycle of the boost control solenoid and it cant run enough duty cycle to make target boost. A manual controller will sort this out lol.

 

Found this picture, the pill is at the compressor end as i thought, ill have a look see if its fallen out or needs to be smaller later (ive been interfering in this area lol.

 

iv always found the pills at the solanoid end but it doesnt realy matter as long as its in the pipework

 

It does, take it to the extreme;
Almost block the pipe to the solenoid= low boost (no matter what the solenoid does, the wastegate will open)
Almost block pipe from compressor to "T"= high boost (if the solenoid is open even minutly it will bleed off ALL avaiable air, resulting in high boost as the wastegate will not open.)
Unless im not seeing it right?

 

your right brain wasnt in gear as im used to working with the 3 port solanoid mostly

 

Just burn the old girl cuz!

 

its ok mate, ive just recieved pink sti 550cc/min injectors and im away to get a td05 20g turbo and programmable ecu for about 360 bhp