Having switched a turbo into my '72 I also put into the dash an after market boost guage. I am getting a reading of 4 off the guage while heavy acceleration. About to add a manual boost controller to get the boost up to about 8-9. Can I really trust the guage to give me an accurate reading throgh the small vac tube attached from the guage to the engine? Seems I will be putting alot of trust in a 50 cent piece of tubing. Thanks

If the tube is nylon, I'd replace it with aluminum or copper tubing as I always do now with the ones that come with oil pressure guages. Yours could result in a vacuum leak but mine resulted in an oily mess behind the dash!

If you are getting a reading of 4 psi, the solution is NOT to turn up the boost, but rather track down why you are getting only 4 psi. Are you running the stock ECU? If so, then you should be getting around 8 psi.

If you do add some more boost, it would be an excellent idea to install an inter-cooler if one is not already installed. Then you can crank that turbo up to peak efficiency without a problem. Plus should give a nice hp increase on stock psi numbers.

I am running the stock ECU and only showing 4 lbs. Maybe the Autometer gauge is not giving me an accurate reading and by adding the controller I may be boosting beyond the capable limit (if my true boost is an accurate stock 8 lbs.) At this time I don't want to add an IC but just add a few lbs. of boost. So to my original question is how accurate are these gauges in determining boost? Are there other options to get accurate readings? Thanks, Steve, for the suggeestion of replacing the nylon tubing with metal. I may do that if no other ideas come up.

The Autometer gauge is probably accurate. If you are only showing 4 psi of boost, then you have a boost leak somewhere.

Where did you tap into when installing the boost gauge? Off the turbo or off the manifold? If off the turbo, you may have an issue with your wastegate/wastegate actuator.

If off the manifold, if could still be your wastegate/wastegate actuator or you may have a leak in the J-pipe or the two connectors (one to the throttle body, one off the turbo).

The stock T3 is capable of safetly boosting up to 12 to 15 psi, but the stock ECU and injectors limit your boost to around 10 psi. Anymore than that and you will start to lean out. You can run up to 10 psi without an intercooler, but an intercooler is recommended even at stock boost levels. You will see a performance difference.