I'm not sure what you mean by before or after the intercooler....for a boost gauge you just need to tee into one of the vacuum lines coming off the top of the intake.
So to answer the question....after the intercooler.
I hooked mine up to the line on the passenger side near the firewall. If you look on the passenger side between the valve cover gasket and the intake there are some hard (steel) vacuum lines bolted to a VC bolt....if you look close to the heater control valve the line changes to a soft line.
Cut that line...add a tee... and run the new boost gauge line behind the engine along the firewall....run it through the hole where your speedo cable goes....under the dash up along the A-pillar to the boost gauge.
VOILA!
Good Luck,
John
