The first SLP lid I purchased for my Z a few years ago fit great. It didnt have sealing issues and never came off. It did rub my hood a little but I could clean it and bam, no problem. So I bought another one for the Ws6 just recently and I def should NOT have. I dunno if it was just old or sat in storage for a long time but man it did not want to go on for ****. It didnt even want to fit onto the front of the MAF, I had to dremel and sand down the inside lip to fit it onto there as if the opening on the lid was not even big enough to go on. Then when I had to fit it flush on the car and clip it in, one side def seals better in the back.
I felt like I paid for a quality slp product the second time and got the china "slc" version instead....
And it obviously wasn't anything I was doing wrong as the first time around, the lid was fine and I always wondered why people had such issues with these things...

They must have two machines that make them and one works like **** or something because it seems so hit or miss with these things.