tuning 91 PA

Is it possible to tune or upgrade a 91 PA engine? I believe HP was increased in '92 or '93 but the engine is still the same? What is the difference or am I wrong?

Not sure what you have, but the 1992-93 came with a 205-horsepower supercharged L67 in the Ultras. The L67 was boosted to 225 horsepower for 1994-95, then the Series II L67 was rated @ 240 horses for '96. Meanwhile, the base L27 engine gained a bit of torque for 1993 & some actual HP with the addition of roller rockers, but had the same 170-horsepower rating. A 205 horsepower Series II L36 3.8-liter V6 became standard for '95.

I have the 91 base model. So it is the roller rockers that make the difference for the 93 base model?