12 inch before the maf would be great. 4 inch is too little. I try and use 7 or more. Good idea too to see what the tuner prefers on the maf. Another choice would be to adapt a lightning maf.
97 Laser Red GT-248A Wingless model, Built Lincoln Mark VIII motor-Procharger D1SC, 3 core IC
2012 Black GT-Saddle, 3.73s, Brembos, Shaker1000