Intercoolers are free horsepower. They also allow you to run higher C/R or boost by cooling down the intake charge while easing the threat of detonation or engine knock.
The stock 930 intercooler (USA '78/9) will hold back a modded engine and not allow all the horses to run free. In my opinion a good aftermarket intercooler is the 2nd most important item to upgrade on a stock USA '78/9 930, the 1st item being the heat exchangers.
If you are going to mod your car in stages here is how I would do it:
#1 - Headers or Euro Heat Exchangers
#2 - Aftermarket Intercooler
#3 - Turbo
#4 - Cams
#5 - Higher Boost Spring (up to 1.0bar)
#6 - Go into the heads/engine and start over at #1
RarlyL8 Motorsports / M&K Exhaust - 911/930 Exhaust Systems, Turbos, TiAL, CIS Mods/Rebuilds
'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
Brian B. (256)536-9977 Service@MKExhaust Brian@RarlyL8