Fitting an External Wastegate and Screamer Pipe

I have been looking at parts that I could fit to a 306 when I get one. My aim is to create one of the best set-up cars in terms of turbo performance and the map that goes with it.
In other words I want to get the very best torque curve and best boost rise and hold as possible.

I have been looking at ways of controlling the boost and the normal ways such as bleed valves and check valves just seem to have too many down sides. One of them being that they creep really easily when you start to raise the boost. This is no good for getting a good rise in boost.

Looking around the internet the best looking option is to go with an electronic boost controller. A lot of modern cars use electronic boost controllers but the 306 HDI's doens't have boost control programmed into it's ECU.
If I am going to get a good controller then I may as well go for a good wastegate to go with it. One that isn't built into the turbo and causing turbulence in the air flow behind the turbo. This is when I got the idea of fitting an external wastegate.

Having looked around on the internet I couldn't find much info. I then decided to look for a 306 HDI exhaust manifold on eBay just to see what would be possible with one. It's then that I noticed that the EGR valve has an output on the exhaust manifold.

306 HDI Exhaust Manifold

Most people when tuning a 306 HDI remove the EGR valve or at least disable it. That means that there is then a free output on the exhaust manifold that could easily be utilised for an external wastegate. Even if an adapter has to be made it won't cost a lot and it looks like it would flow well as well as it is branching out directly from the side of the input to the turbo. Very nice!

Looking on eBay for external wastegates seems to show that 38mm wastegates are the most popular sort of size. It looks as though it would fit quite snuggly onto the EGR flange on the Manifold.

External Wastegate

All being well that would give some seriously good boost control when paired with a decent electronic boost controller. When the fueling gets mapped to the boost levels it would allow for some very good low end torque as the boost will come on quicker and also allow for higher torque in the high RPM band as it keeps the boost pressure under control higher up the RPM range.

Fitting a screamer pipe may make the car a little loud but this would only be when I would be at full boost and almost never really occur at lower engine loads such as everyday driving without full throttle acceleration. If it was too loud then I could always fit a miniature 38mm silencer or something to quieten it down a little.

Screamer Pipe

If it wasn't too loud I could get a pipe made up or even use exhaust flexi pipe wrapped in heat protective wrap and then have it exit the car on a small exhaust tip mounted behind the front right wheel of the car. This would muffle some of the noise as it would be a longer pipe as well.

Thanks for reading.
Jack