AussieSpeed have found that different customers expect difference things from there engines.During the development of our AussieSpeed Manifolds we have found in some engines changing the shape of the plenum can increases torque, horsepower and make your engine produce better torque at lower RPM for better throttle response.AussieSpeed Plenum pigs can be easily removed if your daily drive doubles as you strip stompin weekend warrior.The pig can be fitted to most 2 or 4 barrel manifolds where the bottom of the manifold can be easily accessed. AussieSpeed Plenum Pig inserts sit flat on bottom of manifold & some have molded bottoms to locate in an exact position,Sometimes trimming of Plenum pig or manifold may be required. It is very important that the Manifold and Plenum pig insert are absolutely free of contaminants. These include fuel, oil, sand, filings etc. It is a good idea to use a degreaser or cleaning fluid before installation.It is also recommended that the pig and bolt have a small amount of fuel resistant sealer on the bottom. Once installed fuel mixtures will need to be checked, Due to better atomization in most cases your carburetor may require leaner jets. The pig comes drilled and supplied with 1 bolt,washer and nyloc nut.Some manifolds may require longer bolts when fitting in universal applications.