 Instead of reusing the stock...  Instead of reusing the stock mid-pipe, this particular C5 owner specified TSP's 3-inch off-road crossover X and mid-pipe, which run an additional $349.99. (A catted version is also available for $499.99.) For those who prefer to retain their stock H-pipe, TSP carries catted connection pipes for $249.99. |  After the off-road X and mid-pipe...  After the off-road X and mid-pipe sections are slipped over the headers, the supplied band clamps are positioned and snugged down. The clamps are not fully tightened at this time, as both sections of the exhaust must be installed before finishing. |  The rear connection pipes...  The rear connection pipes are slipped over the mid-pipe. After inserting a cat-back gasket, the nuts on each side are then tightened down. |
 Band clamps are slipped onto...  Band clamps are slipped onto each side of the back section, and the bolts are snugged down. Next come the mid-pipe retainer-bracket nuts. The pipes are then adjusted for a clean fit, and the bolts are fully tightened. A view from the cat-back junction forward highlights the smooth bends in the pipes and the finished system's sanitary look. |  The vehicle is lowered, and...  The vehicle is lowered, and the dipstick tube is reinserted on the passenger side of the block. |  Stock-heat-range NGK TR55...  Stock-heat-range NGK TR55 plugs are installed, along with a set of MSD 8.5mm plug wires to replace the worn factory wires. |
Here's how the engine compartment...
Here's how the engine compartment should look after the installation is complete.
Conclusion
With everything installed and torqued to spec, the vehicle was started and checked for exhaust leaks. When none were found, the C5 was strapped back on the dyno and turned over to TSP co-owner Mangum. After defeating the rear O2 sensors to prevent "check engine" lights, Mangum used LS1Edit to monitor the engine's air/fuel ratio during the dyno pulls. Since this customer was planning to add a Texas Speed camshaft in the near future, no tuning was performed to optimize the exhaust changes.
A total of 28 horsepower and 33 lb-ft of torque was coaxed out of the engine at the peaks. More importantly, the average horsepower and torque from 2,300-5,800 rpm increased by 21 hp and 27 lb-ft. Although the off-road version is a bit louder than stock, the sound isn't raspy or obnoxious, a fact due in part to the Borla cat-back system that was already installed on the car. For an as-tested price of $929.98 (minus labor), the complete off-road system takes a big bite out of the aforementioned Vette tax and performs like the big names to boot.
"Although the headers put out tremendous gains, computer tuning would have netted additional gains on the order of 12-15 rear-wheel horsepower. Since the stock PCM had a slightly rich air fuel ratio of 12:1 and a conservative timing table, gains of more than 40 horsepower [would likely have been possible]. Custom tuning on our Dynojet chassis dynamometer is available, and for customers who don't live in the area, we offer mail-order tunes.
"Using the connection pipes-rather than the off-road X and mid-pipe-typically results in a 4-to-5-horsepower decrease. For those on a tight budget, however, the power gain and resulting sub-$650 price tag are hard to beat. For enthusiasts who want to retain all emissions equipment, the prototype headers with AIR tubes and the catted versions of our X-crossover pipe are showing almost zero horsepower and torque losses over the off-road version tested here."
Texas Speed can handle the installation, tuning, and dyno testing in a day. A highly skilled enthusiast should be able to complete the install in 6-8 hours, but follow-up tuning (either by mail order through Texas Speed or at a local shop) would still be required to extract maximum power.
The Vette tax has been lifted, C5 owners, so get ready to add some big power to your ride.