So you took the end out of the 90mm MAF, jerry rigged it in the 75mm original MAF, which you then reused. The air box is mounted without all the grommets and screw, and the tubing although larger than stock is still reduce throughout. Why did you bother?
You could have got the same air flow improvement out of the original air box by de-snorkeling, replacing the original inlet tube with a 3" smooth pipe with no chambers, and a high flow air filter.
The improvement for this mod come from using the 90mm MAF and 3-1/2" air inlet tube.
The metal above the MAF inlet joint need dented up about 1/2" (Brad Roberts told Kram this needed to be done in his previous posts about this mod) All the screws and grommets can then be mounted along with the 987 MAF. 1, 3.5" coupling sleeve from eBay. 1, 3.5" to 3.25" 90 degree elbow from eBay, 1, 8" x 3.5" aluminum air tub from eBay use about 4", 4, 85mm - 100mm clamps I use 4 stock 987 intake clamps. No glue no epoxy no rigged connector. The tune from a 2004 986-550 Spyder
What isn't mentioned is the cross flow tube need removed, TB needs removed, plenum needs removed, the drive side intake need removed, fuel rail needs disconnected, wire harness needs unclipped from plugs injectors and sensor on the driver side and pulled back. Driver side air grill and the snorkel need removed. before you can remove or install the old air box and the 987 air box. To improve access to the lower part taking off the driver side rear wheel and wheel inter liner help along with the driver side header pipes.
Or remove or drop the engine 2-3".