GQ power increase without turbo

Hi all,

Another question from my best mate who does not have internet access.

He is a very fussy mechanic and I have tried to talk him into sticking a turbo on his 4.2D GQ Patrol but he is also stubborn and we won't change his mind so let's see if we can help.

He has a pretty heavy offroad camper trailer loaded with all of the goodies and is noticing the drag especially on the highway.
He has been advised to remove his injector pump to have it tuned for bit more power by having an enlarged manifold fitted on the injector pump giving more power. They have also advised for him to fit a full 2.5 inch exhaust system to the standard exhaust manifold saying that extractors on the GQ don't make the difference they do on some other vehicles as they already have a semi-tuned exhaust manifold.

He has asked me to post this on here to see if anyone else has heard of or tried these modifications to the injector pump and exhaust. If so any feedback, positive or negative would be appreciated.

He is planning to have the job done in the next week or so before heading off to Darwin and back fully loaded. The total outlay for this job is about $1200. He has said he does not want to outlay the $4500 to fit a turbo and all of the other things that go with it and just wants a little more snot for overtaking etc.

Thanks for your help,

Brett
80 Series T/D