First let me thank you very much for your interest n my problem. I am so glad I discovered this excellent forum.

Compression test has been done and readings are excelent.
Not sure if fuel rail has been cleaned out but I do know a fuel pressure test has been done.
Don't know if exhaust back pressure test has been done but do know that exhaust emissions test has been done and readings are ok.

Is exhaust back pressure test difficult? ... much involved ?