diesel gurus....please help!!!

i need help. if you KNOW what you are talking about regarding diesels, not just what has worked for you, please read and tell me your thoughts!

i went to a "REPUTABLE" diesel workshop in bayswater, asked about putting more boost in my 89 gq 4.2 turbo diesel. it has an aftermarket denco system. the mech lifted the bonnet and straight away tells me that my patrol doesnt have a boost compensator. and further, that it would be this that ione of the problems with my vehicle, as the fuel wont adjust with the boost. he then takes me for a drive in it and says its very sluggish and this would be because of the lack of a compensator. he takes me back to the office and shows me some info that he wrote and was published in a 4x4 mag. he also said that the tappets were noisy and the injectors needed to be done. (even though the guy i bought it off 2 years ago, is a diesel mech and he said he did the injectors just before selling to me) so all up, for injectors, fit boost compensator, increase boost to 10psi, and "tune for 10psi" i was quoted $2650. then that night i went to the berrimah diesel, diesel myths web-page and they state that you dont need one, and that there is very minimal gains to be had for spending $1000-$1800 on a compensator. they say it can be tuned without the compensator. i also read a comment that said if a compensator was needed, then why dont denco, mtx etc fit one as part of their package?

So.............. do i need to go spend the $2650 and have it done by them, or..... should i fit a boost guage, egt and manual boost controller then have it "tuned" (fuel matched to egt) on a dyno and that willl be fine?

please help as the $2650 can be spent elsewhere if its not a necesasary job!

thanks guys!