Replace your stock couplers or use any of these couplers when creating a customer project. 

The Northstar throttlebody to MAF coupler is 3.75" straight. 

The "LS4" couplers are intended for LSJ Cobalts/Ions that install the factory LS4 throttlebody. It is a 3.25" to 3" adapter coupler. Generally the Cobalt uses the 45 degree and the Ion uses the straight coupler.