ok my friend....don't let me discourage you but...the pretty tach. colors and the pretty boost colors are tied into the same unit, assuming you have no aftermarket boost gauge... get ahold of caspers electronics and have it re cal.ed...(maybe $80.00,not sure!) till then i assure you it is no where near accurate with the corrosion and all! your mechanic should/better have a scanner of some sort to, like turbogn said,see what is going on,or you may need to find a different mechanic. those turbo link numbers... i looked into that setup... post what it tells you so i/and more importantly all the others with more experiece can see them and help you with what it shows...i have been thru the backfire thru the intake or the exhaust, i will look into what causes them, i forgot but i had it told to me once what they "may" mean! sorry but i have had a number of probs myself to remember,you'd think i would but i am getting old!...also... turbogn is correct in saying have you ohm'ed or tested the coil paks...however unless you have the caspers tool( i hear there is a way with clear PVC but it doesn't put a load on the paks) to do so, and i do not, it is hard to say good or bad, why(?)(heat &electronics don't play well together!)... i tested my paks and all were good(good=11-13ohm), i also ran it till hot and all tested good again while "hot", but that hot doesn't work(again mine tested good while "hot")... my coil paks were shot, and after replacing them(along with a new module((under paks))) ,problem solved, if you have a friend who had a turbo t or gn try his/hers to see if they work right , if not, you are in my boat, no one to help you out! another thing is the grounds, the biggest problem would be behind the pass. side head, make sure it is not oil saturated and all is functioning well. i had this problem! made a big difference after i corrected this. remember this thing is 18. did you borrow that fuel press. gauge or have your mech. hook one up? if not do so! if so, make damn sure it can be seen while driving to make sure it works accordingly with the boost...every pound of boost increase means it should also increase one PSI!! if not you have a prob! after re-reading this i may have you mixed up with a diferrent post but all the same still apply, sorry if i did so, but like i said it still applies to your condition! let us know what you see/find!