i have a 93 rx7 slightly modded it has full exhaust with high flow cat, front mount and the Apexi f1 commander.Last month the car would start up and run fine for about 15-20 min and then start blowing out black smoke and stall right out. I changed the fuel filter but it still had the same results.So I bring it to Mazda and they had my car for about a month i finally got it back today.On the way back after diving for 15 miles or so I come up to the toll both and it starts smoking like crazy {blue smoke}.Once I get going it doesn't smoke but when i come to a stop or decelerate it'll smoke.It kinda smells of antifreeze any ideas??????