i just got a 3 port race spec, i think i got a good one here. i had a r b concept l2g 5 port and it was hard to break in and i blew it up in 3 races(i want my money back on that junk!!!) . the 3 port was a breeze to began to break in.I also put the extra shim in and took it completly apart and cleaned it out and sealed up, with foil on the head, temps stayed at 200=210. at the 6 tank i was able to drive it up and down my drive way, still fat ( rich ). same for the 7th tank. the 8th tank i took off the foil and temps 200=220 and leaned out the lsn 2 hours. just enough to start a race tune, but still fat and good smoke. the end cause i had to go to work. i still need to put the rest of the break in gallon in the motor befor it is ready. i do know now i want the 5 port race spec motor! 5 port will work better for the two tracks i run on. BUT BOTTOM LINE I LOVE THESE MOTORS!!!!