I used a diegrinder at work. Stuff a rag down the neck as far as you can, but still retreivable. Use an aluminum burr tip in the die grinder and go to town. Dip the tip in oil (or spary with WD-40) every several seconds to keep the aluminum from building up on it. The most important part is changing the blunt inlet end where the neck meets the turbo into a gently tapered "bellmouth". Don't get carried away with grinding a bunch of metal out further down in the neck. Just taper in from the opening. Then use a 1-1.5" or so sanding "flapper" wheel (80-120 grit) in the diegrinder to smooth out your work and polish out the inside as far down as you can reach. I did the same on the outlet side, too, but it isn't as necessary.
Pull out the rag(s) and do the recommended intercooler cleaning and your done!
Hey, while you're at it, grind down the lips inside either end of the up pipe and smooth down the seams on the inside... it's the little things that add up, right?!
"YGETV8" '86 gray T-Type 94K... high tens...?? (STILL "some assembly required"!) Girdled stock block, Stealth turbo, 20 row IC, 65mm "stock" TB, PI 9.5" 7-disc, Jimmy's Trans, P&P heads, 218/218, Hooker Headers, 3" D.P., HKS w.g., thumbwheel chip, and more... (ran [email protected] with the stock long block, DOTs, thru the muff, & on pump gas!)
'86 GN "Beater"... 137K driver w/ P&P stock turbo, 21.5 psi boost, K&N, 3" DP and ported elbow, 93 chip, 30# inj., Walbro 307, AFPR, new valve springs, alum. drums, 2.5" IC neck, 62mm TB/upper, and that's about it! Best ET: 12.61 (on 215/65 all season radials!); best MPH: 111.97!
'87 WE4 59K ... GNX wheels, 93 chip, ported stock turbo, 21 psi boost, AFPR, Blue Tops, Borla exhaust, K&N, alum. drums... 'bout it! [email protected] on 265/50-16 radial TAs on it's maiden voyage to the track!!
IMO the stock neck is so poor to begin with that it makes more sense to just saw it off and install a better one. If you are resourceful this can be done for about $60 or so and the results are better than trying to port the existing neck, which makes a sharp, very small diameter, > than 90 deg turn.