...after which the silencer assembly and intake tube lift off of the engine in one piece. | 
Now simply unclip the filter retainer clips and pop the filter box's lid off. You can see the MAF through the inlet tube opening, and also note that the panel-style paper filter included from the factory is very coarsely pleated-not exactly the optimum setup for surface area. | 
With the stock filter out of the way, we note that the lower airbox shell (which is reused with this GMPP kit) pulls its air from a tube leading down and forward to the area beneath the headlight. There's actually a full separate silencer down there, but getting at it pretty much requires pulling the front bumper cover off, so you'll have to wait to see it until our next issue (when we yank the bumper cover and install a sweet ground effects kit complete with in-fender external DVD screens). Seriously though, we've seen it-and it's a free- flowing, nonrestrictive piece, so there's no sense in getting down there and ripping it out. |
Time to begin assembling the new intake. Slide the conical GMPP filter onto the neck inside the new airlid, and after rotating to establish proper clearance about the filter (the filter is not symmetrical about its inlet), tighten the #48 mounting clamp. This new open-top lid will seal to the underside of the hood, a methodology that's much better than having the filter exposed to hot underhood air. We'll see if hood-open and hood-closed dynos show a difference. | 
After clipping the new lid to the stock airbox bottom, cut and install the supplied trim material about its upper edge. This should form a tight seal with the hood/hoodliner. (Attempts to close the hood with myself inside to verify this were unsuccessful.) | 
The MAF on these cars is a blade type, as is the trend with today's GM engines. After removing the two stock Phillips-head screws holding it into the stock airbox lid, carefully slide the MAF out and transfer it to the new polished GMPP intake pipe. Secure using the supplied 2.5mm Allen heads, but don't over tighten! |
Assemble the intake hat and appropriate rubber couplers onto the polished intake tube, but leave the clamps loose for now. The hat/tube assembly will now go onto the car as one piece, but before doing so, install the section of orange adapter hose onto the throttle body (bottom left of photo). This will allow the plastic intake hat to grab and seal onto the perimeter of the throttle body opening. With this done, the intake assembly goes on, noting that a good amount of adjustment will be needed to achieve proper pipe orientation. Keep an eye on clearance with the upper radiator hose. | 
Once you're satisfied with system adjustments, tighten the clamps. After plugging the MAF back in and installing the supplied PCV hose between the polished intake tube and the valve cover, apply the supplied decals (including the CARB E.O. number appliqu) and you're done! We're now treated to a much-improved underhood appearance, and we'll defi- nitely be leaving off that other engine cover. Time to hit the Dynojet again, but a quick note first. While we were on the dyno, we experimented and covered the intake top with a piece of cardboard to simulate the hood being closed, and found that the intake gains were roughly cut in half-an effect that would likely be alleviated or cancelled out completely with the car moving down the road (thanks to the added motion of air about the front body panels). Our final number quoted is without cardboard, however. | 
The GMPP intake picked up another 6.8 horses and 4.6 lb-ft, leaving us just shy of 149 fwhp and 140 fwtq (blue graph; all-stock is in red). Note our overall power gain with the GMPP intake and exhaust translates to roughly 5.8 percent, which on a 300-rwhp LS1 F-car would have bumped things up to over 317. That's pretty good for some simple bolt-ons! Also notice we're still seeing a slight reduction in AFR; assuming the readings were correct, it would appear custom tuning would help even this out, and bring additional gains over the factory calibration (tuning is by no means mandatory with these GMPP bolt-ons, of course). |