Our original intentions were to test both types of mufflers on the X-pipe, but we declined after the Ultra Flo results. The collector-reducers were also previously coated with anti-seize to ease swapping the H- and X-pipe. Besides, tti's components have always proven to provide ease of installation and fit. Next, the tti modified-to-fit UltraFlos were hung in place and attached to the X.

After firing up the mule with the X-pipe, we noticed a quieter, smoother sounding exhaust note. All present commented the X-pipe produced a more pleasant tone. Remarkably, the X-pipe seemed to slightly smooth out the idle and throttle response. This was confirmed with a best, for the day, 1.56 sixty-foot time. Ironically, the quarter-mile e.t. was nearly identical to the H-pipe. At this point, the ambient temperature was up to 82 degrees. We were happy the X-pipe was helping the R/T go as fast as the H-pipe, but with a smoother idle, better throttle response, and less noise (decibels were down to 97), we couldn't go wrong.

Satisfied with the results, we packed it in and called it a day. Many X-pipe converts will notice their engine A/F will richen up. After a plug check we didn't notice any difference. An effort towards leaner jets was an afterthought for another day. This would enable us to install the tailpipes in the comfort of our home garage.

X-Back Track
Once back to the track, we were faced with a day showing more heat and humidity along with a lower barometric pressure. To a drag racer this only means a slower car. The unfavorable air slowed the baseline a tenth to 11.11 at 121.10 mph. One of the benefits of having a complete exhaust system-the R/T was now two decibels quieter with much less interior noise.

On this sultry day (86 degrees, 73 percent humidity and 29.80 barometer), we next decided to try leaner secondary jets (from 78 to 76). We thought on this bad air day that leaner would be meaner; instead we slowed to an 11.17 at 120.62. Apparently, our wedge wanted more fuel. Would a move to 80 secondary jets help?

Back in the pits, we upped the carb mixture on the Holley HP in a last ditch effort. Testing with worsening weather conditions, even with one-hour cool-downs, is not advantageous when considering engine heat sink. Out of the hole the 60-foot e.t was back, and the quarter e.t was only two hundredths faster. At that point we decided we would try tuning our combo on a different day with better weather conditions. We learned from testing the importance of matching tolerable exhaust tones with desirable performance gains, while finding that happy medium.

Conclusion
The X exhibited a nice, new sound, while still sounding like a rocking big-block. With three less decibels, the quieter tti X-pipe is there to stay on the R/T. Even though our combo didn't e.t. any better with the X-pipe (possibly because of less than favorable weather conditions when tested), the idle and throttle response feels smoother and stronger. The big surprise was the muffler swap; the UltraFlo's are definitely an improvement. We were impressed at how the X-pipe and Ultra Flos teamed up to give us our best 60-foot and quarter-mile e.t ever; this on a day that was thirty degrees warmer.