I see a lot of post about PIP and have experienced it myself. My ex wife is a RN and has administered more shots than anyone I could possibly know, so I had a discussion with her on this in an attempt to learn straight from a very experienced source.
I'm personally 3 weeks into my first Test E cycle and she has done all of my injections except 1. The 1 I did myself hurt like hell for about 3 days. All of the previous injections she had done for me had 0 PIP, none at all, couldn't tell anything had happened. That's what triggered me asking her.

It all comes down to location. Certain areas of the body are more prone to PIP than others. Quad is probably the most sensitive muscle to PIP in the body. She told me that she never administers any sort of meds through the quad, doesn't matter what it is, it's going to hurt every time. Being an RN, last thing she needs is a patient complaining about something else. Her preference is to do injections in the Ventrogluteal Muscle. Gluteal obviously being in the butt. Use a chart to find the muscle, it's small. If you look in the mirror and put pressure on your leg, you can see a small muscle pop out just at the top of your butt on the side, up closer to the waist line. This is where she has done all of my injections and I don't feel a thing.

So if you're fighting with PIP, I highly suggest you find this muscle and give it a try. You can thank me later.