Almost any exhaust will require a tune, only exception is the Cat free UP pipe to the turbo.
The Oil/Air separator will work well if you can plumb all the hoses right. Any oil that gets sucked into the PVC system dumps it right into the turbo intake and blows it right into the intercoolers vanes. GUMMY MESS. It also lowers the octain of the air/fuel mix.
Most cold air intakes will require a tune too and really does nothing at less that Stage 2.5 or 3 and above. It does make the car LOUDER inside the cabin.
A bigger intercooler will also require a tune due to a denser air and a lean condition. I am working on a air temperature switch/relay that will turn on a "SPAL" style fan above the intercooler to blow air down to remove heat soak. I have a 8 inch fan that fits on top of the intercooler but getting it vibration isolated and sealed is still in the works. It can not vibrate on the aluminum of the intercooler or it will wear a hole quick. I found this out on my 1994 Legacy Sport Wagon's turbo's TMIC. I also had a spray bar that sprayed cold water/alcohol on the top of the intercooler. A 3 gallon tank with 2 quarts of denatured Alcohol, a bag of ice or dry ice and a small water pump. I only used it on hot days when I need a hard boost. Dry Ice is very cold but also dangerous in an enclosed cabin or trunk of a sedan. It displaces oxygen with Carbon Dioxide.
These are my opinions based on a 1994 2.2 turbo with a lot of WRX and STI parts.
The Oil/Air separator will work well if you can plumb all the hoses right. Any oil that gets sucked into the PVC system dumps it right into the turbo intake and blows it right into the intercoolers vanes. GUMMY MESS. It also lowers the octain of the air/fuel mix.
Most cold air intakes will require a tune too and really does nothing at less that Stage 2.5 or 3 and above. It does make the car LOUDER inside the cabin.
A bigger intercooler will also require a tune due to a denser air and a lean condition. I am working on a air temperature switch/relay that will turn on a "SPAL" style fan above the intercooler to blow air down to remove heat soak. I have a 8 inch fan that fits on top of the intercooler but getting it vibration isolated and sealed is still in the works. It can not vibrate on the aluminum of the intercooler or it will wear a hole quick. I found this out on my 1994 Legacy Sport Wagon's turbo's TMIC. I also had a spray bar that sprayed cold water/alcohol on the top of the intercooler. A 3 gallon tank with 2 quarts of denatured Alcohol, a bag of ice or dry ice and a small water pump. I only used it on hot days when I need a hard boost. Dry Ice is very cold but also dangerous in an enclosed cabin or trunk of a sedan. It displaces oxygen with Carbon Dioxide.
These are my opinions based on a 1994 2.2 turbo with a lot of WRX and STI parts.
