As expected, the torque curve was broad, peaking at just 3,000 rpm. Torque production exceeded 200 lb-ft, from 2,000 rpm to 5,000 rpm. In the meaty part of the curve, the torque production exceeded 250 lb-ft, from 2,300 rpm to 3,400 rpm. The stock motor wouldn't rip off your head with accelerative forces, but it still managed to get the big car moving onto the local freeway with vigor. It's not ready for a spot on Pinks, but neither is it ready for the slow death of the wrecking yard.
The first modification was to replace the factory flat-panel filter with a free-flowing K&N unit. The filter swap netted some impressive torque gains, especially in the low and medium rpm ranges. | 
T-Bird Super Coupe: Stock vs. K&N Filter
Not having proper data logging during this testing, we suspect that a portion of the impressive power gains illustrated by this simple filer change can be attributed to a slight change in running tempera-ture. We made every attempt to maintain a constant start temperature, but the factory gauges are not exactly what you would call precise. Obviously the factory flat-panel filter (or at least our high-mileage unit) was restrictive to the motor. We showed some impressive power gains with the filter change. This gave us hope that we may reach our goal of 300 rwhp with this supercharged 3.8L. | 
Given that the motor was equipped with a supercharger, we naturally wanted to increase the boost pressure. Super Coupe Performance supplied a 5 percent overdrive pulley for the Eaton supercharger. The blower pulley offered an increase in boost of 1.5 psi and another sizable power gain throughout the rev range. |
With our baseline numbers repeating nicely, we ventured into Super Coupe performance land. Starting at the beginning, we replaced the stock flat-panel air filter with a K&N unit. We all did this to our 5.0L Mustangs back in the day, and for good reason. The factory filter was pretty dirty, and replacing it with the free-flowing K&N filter netted an impressive power gain. It must be stated that we did not have access to the usual array of data-logging equipment for this dyno session and had to rely on the factory tempera-ture gauge to ensure we started each run at (or near) the same coolant temp.
After replacing the stock filter with the K&N, the power jumped from 192 hp and 265 lb-ft of torque to an even 200 hp and 287 lb-ft. As always, we included graphs to properly illustrate the power gains, since peak numbers tell only a small portion of the story. The new filter added sizable gains in the low and midrange, but little or no power at the top of the rev range. We suspected that some of the torque gains could be attributed to a change in temperature between the runs, but a back-up run (with the stock filter) brought us back to the original power numbers. We guess the K&N panel filter is a worthwhile upgrade on the Super Coupe, especially since it ensures cold air to the motor when the hood is closed.
Wanting to maximize flow to the blower, we removed the factory mass airflow meter. | 
SC Performance's 5 Percent Blower Pulley
The next modification was a surefire route to improved performance. Super Coupe Performance supplied one of its 5 percent overdrive blower pulleys for the stock M90 supercharger. Increasing the speed of the blower increased the boost pressure to the 3.8L motor and improved the power output right along with it. Notice that the increase in boost pressure added power throughout the rev range. | 
C&L 73mm MAF And Cone Filter
Knowing that positive-displacement blowers are sensitive to inlet restrictions, we replaced the factory MAF with a larger 73mm unit from C&L. C&L also provided the necessary K&N cone filter (as well as the flat filter used in the first test). Replacing the stock MAF with the C&L improved the power output by 7-8 hp, with most of the gains coming at the top of the rev range. |
Having improved the inlet flow of the system, we decided it was time to crank up the boost. This was accomplished by replacing the factory blower pulley with a 5 percent overdrive pulley from Super Coupe Performance. Bill at Super Coupe Performance was instrumental in getting this T-bird project off and running. Replacing the pulley required removal of the pressed-on factory pulley. Bill supplied a removal tool (basically a backing plate to be used with a three-jaw puller) that made short work of the pulley swap. After the installation of the smaller blower pulley, we were rewarded with roughly 1.5 psi of extra boost and a sizable chunk of torque to go along with it. The supercharged 3.8L had now officially cracked the 300 lb-ft barrier, with a peak torque reading of 309 lb-ft. Torque production exceeded 300 lb-ft from 2,100 rpm to 3,200 rpm and didn't drop below 250 lb-ft until 4,300 rpm, but we were just getting started.