As far as I know pro stock drag cars do not. That shows what Yellow Rose is saying. I wish I had all the time and money to get every last ounce of power out my car but I don't. I'm like most hobby guys, I build my own engines and do my best to choose parts that work well together without cashing in my kids college savings to build them. If I can spend less than $20 on a crutch that makes the car faster and sound better I'll do it. Thank you Yellow Rose for the info, the more we know the better off we are.