Once we lifted our '85 4Runner and slapped a meaty set of 32s under the fenders, the little 22RE four-cylinder threw in the towel. It was like it wasn't even trying anymore. Since gears are still on the horizon, we decided to step up to a Downey chrome 4-into-1 header and 21/2-inch exhaust system to try to regain some lost power.
Header
The header kit (PN 1741081) comes with everything you need. That includes a new chrome-plated header with a 3/8-inch flange and block-off plates for the air-injection manifold, a thicker gasket, a new downpipe, and a collector with provisions for hooking up to your stock catalytic converter if you don't plan on using the 21/2-inch exhaust kit.
Exhaust
The 21/2-inch aluminized exhaust (PN 17432) includes all the pipes needed to route your exhaust from your new header back to the stock location behind the rear tire, a high-flow Downey muffler, and a high-flow 21/2-inch-diameter catalytic converter. There are also several different O2 sensor locations to accommodate different engine and body styles. Block-off plates are provided for those that aren't needed.
Installation
Downey supplies instructions, but it's basically a cut-to-fit affair using the supplied pipes. It took about 30 minutes to remove the stock system and two hours to install the Downey header and exhaust. Actually, this was the easiest header installation we've ever done. It dropped right onto the engine with no interference from steering or suspension components. The exhaust was easy to install up to the catalytic converter, but the pipe that goes from the rear of the cat to the elbow pipe in front of the muffler hit the floor no matter how we jockeyed it. We left it alone, thinking we'd fix it later, but it doesn't rattle at all and it doesn't heat up the floor, so we'll keep it where it is. While our stock tailpipe exited behind the spring shackle, the Downey tailpipe exits in front of it, but it clears even at full droop. If you've got a 4Runner and are still running the goofy plastic cladding, you'll need a turndown pipe (PN 17432). Our is gone, so the pickup exit location works fine.
Performance
Well, it sounds like an angry Honda now, but it feels like there's a lot more mid- and upper-rpm horsepower. Passing can be scary at times, but that's an improvement over not being able to pass at all. Our average mpg also increased from 15.58 to 17.38 with a lot of full-throttle use. But the best part is that we were able to replace our poor-performing, rotted stock system without the expense of a muffler shop.
 01. The header install is...  01. The header install is a slam-dunk. Just slather the Downey header gasket in Permatex hi-temp copper RTV, install the air injection manifold block-off plates (if yours needs them), and torque the bolts to 45 lb-ft. Use the supplied O2 sensor gasket with no silicon and reinstall the O2 sensor. |  02. The new system should...  02. The new system should flow way better than the stock system. We were worried that the monstrous 21/2-inch tubing would totally kill our bottom end, but our fuel-injected engine feels the same at lower rpm as before, and stronger in the mid and upper ranges. | 
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 04. You've got some options...  04. You've got some options and Downey's instructions cover almost all application possibilities. You can see where the exhaust contacts the floor behind the cat. We used the original rubber isolators to bolt to the pipe behind the cat. Check out how the elbow clocks the muffler up and away from trail obstacles. |  05. Our tailpipe wound up...  05. Our tailpipe wound up being rather close to the shackle, but it hasn't been a problem yet. Since the exhaust system bolts together, we can always remove the tailpipe and cut off an inch or two to move it forward if the suspension becomes suppler over time and begins to tag it. | |