Wouldn't say I felt a massive difference, however I did notice a smoother idle and a little better throttle response which is exactly why I bought this. For the price you cant beat it.

This product was a great fit and is well made

I bought the frx and the hpx at the same time. I install the frx first because i wanted the fuel pressure. And to hear the difference between the two products. When the hpx was installed the truck at idle ran very smooth. And when driving it seemed to rev easier. Great product!

This thing kind of helped, after initial run in time when I start the engine it is quiet but after about a minute it starts making the 7.3 knock again sometimes its louder than others but that is what I was trying to eliminate I listened to it for 13 years and thought I finally found the answer to the injector knock (sounds like somebody is banging on the block with a ball peen hammer)
Anyway it kind of works

cheap and easy to install. makes quite a difference in sound. idle is much smoother as well. even at cruising speed it seems to have made a difference as well. recommend doing!

I had a leaking turbo pedistal so I figured I might as well install this while I was in the engine bay! All I can say is this product is built extremely well, and greatly reduced my injector noise, my truck has 330,000 miles, and has never started up easier! Well worth the money

I ordered an FRx and decided to add this to the order too. I was hoping to add things to our engine that would allow it to last longer. It currently has 135,000mi. After lots of reading, I purchased the pair. I noticed right away, the sound change of the motor. When cruising at 80mph or even 75mph, it's quieter in the cab. My wife asked what I did, because it was a smoother ride and quieter. I felt it in the steering wheel and seat. It seems to run now like it should have always been from the factory. Well worth the money. Plan on buying another setup for our farm truck and add the CVD fuel fittings to the order.

Very glad I added this to my 99 7.3, help smooth out the running and seem to give a noticeable difference in the throttle response.

Easy install, a must have for 7.3.