@Xulfiqar
Thanks for starting this thread and I hope you are still looking at it time to time.
I have an 80 series with 1hdt engine... long story short it was in weak health at the time when I bought the car and after going thru several workshops we decided to get it rebuild because everyone recommended that. A couple of workshops also recommended to swap with some other used engine but I didn't want to get into same loop again so I went ahead with a rebuild. The rebuild work was done good because it was done in front of my father who has 30+ years of experience in machining and fabrication.
The car was much better after the rebuilt but the power and torque was not justified enough coming from from a 4.2 liter engine with a turbo. So I went to same workshop and other workshops and diesel labs to find someone capable enough to tell me why I don't have the grunt that I am expecting from my engine.
After getting dissatisfied from everyone, now I have decided to work upon my engine myself to every possible extent. I am utilizing ih8mud, lcool and youtube so far and now I just found this thread where I can possibly find the answers I am looking for as well.
There are only a few things I have done myself considering the condition of my engine. The current clock is around 40,000 km after the rebuild. There is a black puff when you start the engine which is fine I guess. It starts really quickly at half self almost. At idle there is no black smoke coming out. Around 3000 rpms I see some black smoke coming out at which I reduce my rpms again because I cant bear that sight. I get around 9 kmpl combined fuel average which is good in my opinion.
I didn't know where to start from so I decided to work on the exhaust, I removed the old exhaust pipe and muffler which was 2 inch pipe pinched from almost 3 places and replaced with a free flow 3" stainless steel pipe (muffler deleted). Its not sounding so well but I am ignoring it for now. After the 3 inch exhaust I found my engine response to be a bit better but nothing close to what I expect or I see in Australian 4wd videos.
The second thing I did was to install a pressure guage to check turbo boost pressure. I got really disappointed as the max boost I could get was only 5 psi at 3000 rpm. I have installed a 30 psi guage in hope that one day I will be running 20 psi 
. At 2000 rpm I hardly get 3 psi when pushing hard. When cruising I have something between 0-1 psi depending on speed. I think they are really low figures even for the stock settings.
The third thing that I have done so far is adjusting the off boost compensator fuel setting. I made these adjustments by the screw located on the top of boost compensator. As I saw on the internet that if you turn it full 360 deg it will come back to the same position where i started so I just turned it 180 degrees to see what effect it makes on the fuel settings. After the 180 turn I observed that my idle rpm was increased to 1000 from 700 which I reduced to 700 again from the accelerator pedal adjustment. After doing this adjustment I felt my car to become more responsive and much better in 1st,2nd and 3rd gear. To test that I took my car to slopes, the performance was ok but I could not accelerate much in 3rd gear and 2nd gear is too slow. A 660cc car would easily cross me on any slope. so in short the fuel adjustment thing did something good but it didn't make things anywhere close to perfect.
After doing the exhaust and off boost compensator setting I don't see any black smoke at all during the driving, even at 3000+ rpm, no black smoke at all.
Sorry for posting a long one but I want your suggestion and suggestions from every one what should be my next move. How should I tackle my low boost on turbo?
Above all that I have a bigger issue as well. I am running 31 inch tyres and at 2000 rpm I get speed of 62 km/hr in 5th gear. I have no idea whats wrong here as well but i don't wanna open too many things together. I need suggestions for that also.
Cheers
