When you guys are doing a boost leak test do you cap off the intake manifold or not? What do you do about pressurized air leaking out the exhaust if you don't cap off the I.M.

 

i would assume that the closed TB blade would cap it off enough

 

Not exactly , The TB blade is closed BUT the idle control valve(sensor or what every it called) lets air go into the motor so it can idle .

If your motor is warmed up and its @tdc it should hold psi , but if still not working for you , can take off of the TB elbo and plug it (i use a empty spray paint can ) . BUT the psi gauge in the car wil not work so you have to use a nother psi gauge (ei tire gauge) .