Exactly right...its the spark plugs, get some .7mm gapped plugs...my friend spent BIG $$$ and it ended up being the plugs, its like Popping sound with more than 11psi. He changed plugs and now its gone...
Get some good platniums or iridium IRIWAY, pm me if ur want heat range 7,8,9 or 10 (true racing plugs, which no one will stock, except performance places. about $28.00 each but more than perfect and last 80-150,000km)