The exhaust is split out of the muffler, not behind the Cat. The exhaust manifolds in 98 were the same for all models. Not different for the SSEi. The SLE and SSE got the same exhaust as the SE, only the SE was single outlet. We have one car here that came from the factory as a Supercharged SE, but it came with the full blown L67 top to bottom, minus the boost gauge. The classic sleeper. Belongs to 95BonnevilleSESC.
Here'* a list of everything different between the SSEi and other models that weren't supercharged:
Forged crank/rods/pistons, heads, lower intake, supercharger, wiring harness, pcm, transmission, boost gauge, a bunch of vacuum lines, and on and on.
You can't do this. You could sell the car and use the cash it would cost plus what you get for your 98 to buy a brand new SSEi. Start thinking NOS, a Turbo, or an aftermarket centrifugal supercharger.
Or swap the entire drivetrain, wiring harness, and PCM.
They really are two different animals.
Welcome to the forum! I think you make the 6th or so in Ohio. You guys have a reunion lurking just over the horizon!