Is the Spintech the only company that makes a muffler with a 4 inch inlet and 2 three inch outlets for our cars?

 

Not in the splitcase configuration, IMO if you're looking for higher flow Magnaflow has several model that might meet your needs.
# 12594 (4"in/dual3" out(same side) oval case), #14153 ( 4" in/out oval case), #14163 (4" in/out 6" dia. case). price range is $130-$155.

 

OK, thanks.