TQs30z

Hi Guys, my 260z has some weird and loud knocking noise coming from the motor. I don't know whether this cause it or not, here you go: I take my car for a spirit ride I'm doing 70mph in 4th gear in 4k rmp for for about 7sec and slow down after that. The car run fine after that. However, after a while, the car start making weird knocking noise, and it keeps backfire at the exhaust when after I release the gas pedals. At first, I thought it is some kind of exhaust leak or something, but after I pull over and poops the hood, the noise is coming my the motor, especially from cylinders that closer to the firewall. Any suggestions what's going on?? I'm thinking about the valve hitting the piston, but not sure though, any helps are appreciate, thanks. Ed

Some JDM parts and hard to find parts for s30. Also, you may need a decent looking website for your import and export business. Just my .02 and good luck! Ed