After taking advice from forum members, I took off my JL-Motoring VRS Style Type II Rear Diffuser (it was already falling off from the 3M double-sided tape), and re-did the install with epoxy.
I bought Loctite Plastic Epoxy from Home Depot. You will need to buy two.
It has a 7 minute cure time, so you must work fast. I highly recommend having two people apply simultaneously the epoxy. I made the mistake of applying the epoxy to the diffuser myself and it was curing quickly and was very rushed. I did not have time to apply the epoxy to the very thin edges of the diffuser along the sides. That is why I have a small gap...see pictures.
I also bought two 1" Husky C-Clamps and two 2" Husky C-Clamps from Home Depot. You will not need to use the 2" C-Clamps, so do not bother buying. Be sure you use tissue paper to tape up the end of the C-Clamp as not to scratch up the diffuser.
Prepare the diffuser by masking taping several lawyers of tissue paper along the far sides of the diffuser. I also taped the center portion with tissue paper, but during the install, found out it was completely unnecessary:
If you have removable tips on your exhaust (like the AA Signature does), remove them.
Squirt both packages of the Epoxy into a plastic disposable bowl. I used a plastic disposable knife to mix the solution. Once it was mixed, I used the knive to apply the epoxy along ALL edges of the diffuser (except the rear edge new the slotted tabs. Be absolutely sure that you apply the solution to the very thin edges of the diffuser (where it curves)...this is there area that is prone to gaps. Also, be sure to apply the epoxy not only on the flat portion of the diffuser (the grooved section) and a little bit where the grooved portion transitions to the carbon fiber. You need to be careful as epoxy gets very HOT when the two components of it are mixed and you only have about 3 minutes to work before the epoxy starts solidifying. Therefore, you'll need TWO people to help you apply so neither is rushed.
At this point, you'll need a total of THREE people. One person is going to get underneatht the car to make sure the slotted tabs of the diffuser are aligned with the OEM screw holes. The other two should hold the diffuser on the left and right side. Position the diffuser in place and the person underneath the car should line up the screw holes and place the screws VERY LOOSELY, just so it is aligned. The person underneath should now quickly come out from under the car and use the 1" C-clamp to clamp the diffuser as shown below, on both sides:
Once both C-Clamps are secured, the person who installed the C-clamps, should get out 3M masking tape (I used 2" width). And begin taping the diffuser to the rear bumper. Be sure to pull the tape highly taught and lift the diffuser as you do this. The result should look like this. Notice how tight the masking tape is. Do however, be sure that that stress created by the masking tape is evenly applied so that the rear of the diffuser is completely horizontal with the OEM bumper.
When all the masking tape is applied, by this time, the epoxy should be cured. You should now tighten the two OEM screws. The reason for NOT tightening the OEM screws in the beginning, is because if you did, you would have absolutely no wiggle room (without creating extra stress) to press the diffuser to the bumper.
The epoxy instructions says to wait for 24 hrs. I did not. I checked on the car after about 17 hrs and everything seemed to be solid. Remove all your masking tape. There will be some sticky residue all over your bumper and diffuser. Get some Goo-Gone to remove the residue. Get some spray detailer and whipe off the Goo-Gone.
I noticed that the center of the diffuser is installed slightly higher than the left and right sides. I think in the taping process I had too much stress and was pulling the center portion of the diffuser way too high. So make sure that the stress of the tape is applied evenly all across the rear edge of the diffuser.
Slight Gap on the top:
Slight Gap on the top:
AA Signature Exhaust Tips Added:
Overall, I the JL-Motoring Rear Diffuser does fit decently. Whether or not you get gaps at the end of installation, is completely dependent on the quality of the install. This was my first time installing this diffuser with epoxy. If I could do it again, I bet I could install it perfectly, as now I know what to watch out for. I do recommend the JL-Motoring VRS style Type II Rear Diffuser as a cheap alternative to an authentic VRS. It may not install as easily as an authentic VRS, but I don't see paying an extra $450+ to get an authentic VRS.