I too made up a 4 inch intake. Bought necessary parts from
http://www.airflo.com/. The critical, hard-to-find part is the elbow to the throttle body. I used a 90 degree 4" to 3.5" elbow.
I already had a Lingenfelter and used some of the Lingenfelter parts, namely the short silicon hose.
I removed the screen on the MAF. Note, the Corvette has no such screen, probably because intake air makes a straight shot to the MAF from the air filter. On the CTS-V there is a 90 degree bend from the air filter to the MAF.
I moved the MAF closer to the throttle body, and attached it to the 90 degree elbow. Now I have at about 12-15 inch tube before the MAF to straighten air flow.
It is unlikely that any aftermarket mfg will try to market the MAF relocation as it required me to cut in an extension five-wire set to the MAF. The plugs to the MAF are proprietary, and will be very hard to find and purchase. Hence, I don't see an aftermarket mfg trying to relocate the MAF because they will not be able to offer an extension wire set. I tried to attach a photo, but could not because my photo file is too large. I will email photos to Reed.