i have audi a4 b5 1998 1.8t automatic. i change the stock dv to the forge splitter and i set 100%bov. for the first week it runs good and no problem. but on traffic stop and go, sometime my rpm drop very low and causing engine stall. the check engine light also showing. is there anyway to fix this?

 

Yes, stop using a blow-off-valve on a car not designed to be run with a BOV.
You are doing permanent damage to your engine - you should check your tailpipes, if they are getting sooty inside, you are ******* your car.

 

I think you are probably throwing off your air/fuel ratio too bad by using the BOV. From what I understand A4's predating 2000 won't work well using a BOV.

 

The RPM drops becuase the valve is not closeing fast enough or at all. Do you have a boost gauge? I have a type s BOV and had this problem to. The valve wouldnt close fast enough and the RPM would drop. What i did is adjust the BOV all the way down where it will close at idle. Never had a problem sence. I read that it will run rich between shifts. I have an auto so no problem there. No smoke no sutt no nothing.

 

BOVs for the lose.

 

you can use a BOV without problems if its adjusted correctly and closed at idle. most people have a hard time figuring out how to do this, which is why a DV is a better choice. there is no performance gain using a BOV vs a DV on the stock turbo. unless you have a real reason to use one, stick with a DV so i dont have to keep reading these threads.

 

adjust the thing. and i agree 100% with ghost6303

 

No... because your MAF measures the air the car is taking in and it does not account for what the BOV is blowing off.

 

how to check the tailpipes?

 

Running rich (because the BOV is letting off air that the car thinks it should be using) should make the tailpipes unusually blackened (like soot inside them). But a high mileage car will likely have blackened tailpipes anyway.