Í just installed the a metal pipe intake kit from ebay on my FD...its the same metal pipe kit found for the intake piping on rx7store....everything fits fine

Problem is, i Have 2 hks universal 3inch opening Super Power Flow Hex intakes that I want to fit on the pipes but the pipes are both 2.25 inches in diameter...

I am looking for some type of reducing coupler...on ebay the lowest the couplers reduce are 3>2.5...will the use of clams allow me to reduce the 2.5 inch end down to 2.25 so that they fit the piping or should I search for expensive silicon 3>2.25 inch couplings?