[ted frater]

I picked up a spare cyl head for my Vitara 1997 5 door diesel . Thats with the Mazda 2ltr,mr turbo intercooled motor.
This head had done some 121,000 miles and the inlet ports, manifold , and post egr valve section of inlet was severely coked up with oily exhaust gas carbon. About 1/8 in thick in places.
My motor has done only 83,000 miles and as far as I can tell, has never been apart.
One of the things I did some 3 months ago was take off the intercooler and have a look see inside. all oily, so i washed it out with petrol several times. Lots of oily residue from that.
After I got my vitara some 9 months ago, on adviceof a friend I blamked off the EGR valve in my programme of engine efficiency improvement. As anside that has certainly made a noticeable difference in fuel efficiency.
so i expect my inlet ports etc to be somewhat fouled up but by no means as bad as the sparechead Ive here.
Now, the question is,
When off boost from the turbo, how much efficiency am i likely to lose with
a dirty fouled up inlet system?
Ive always thought that its important to keep the inlet system clean and smooth
to get the best cyl filling possible, especially on a diesel, where one is always looking for the max amount of clean cold air getting into the cylinders?
Any thoughts or advice welcome.
Ted
In Dorset
UK