4 stroke engines do not, but 2 stokes heavily rely on a properly tuned exhaust!AMEN- Aidan
There are countless engineering papers written on this subject. Engines don't want and don't need backpressure.
During the very early years of development a few gas engine EGR systems relied on backpressure for proper function. I think that is where this misconception got started.
But thats a totally different subject.
Any ammount of restriction after the turbo is only going to increase lag and EGTs, open'er up and let'er breathe!