Exhaust back pressure in tuning

I was wondering what would be the reason for implementing a backpressure sensor in your sensor arsenal and what are the tuning strategies that can implement them?

If you mean exhaust manifold pressure for turbo-charged engines, if you monitor the pressure there, and compare it to the intake manifold pressure, you can make a good estimate if the turbine and/or housing is to large or too small. If the first, it may be slow to build pressure and have a low exhaust:intake ratio, whereas if it is high, you will be losing power and efficiency because the turbine is choking the engine and it will also be increasing the probability of exhaust remaining in the cylinder which means less charge to burn.

If you have a series of sensors, you can analyse the whole exhaust system to see where the main pressure drops are - in theory, you want it all across the turbine. If it is practical, you may also find a turbo' speed sensor worthwhile, to go with the exhaust temperature sensor.

Mr Gale Banks did a feature on this a few weeks ago - it's a diesel engine, but many of the principles apply for both engine types and you could do worse than watch all his other videos too - https://www.youtube.com/watch?v=E8sm0c_kSh8

You can obviously use IMP:EMP as the main load scale in a speed dendity system too, this is more robust than intake pressure only speed density as it will compensate for changes in altitude or if intake or exhaust problems develop such as dirty filters or colapsed catylists/mufflers/flex joints.