hi there, i am running a 3.9 in a 90 and used a janspeed which had just the one box tucked out of the way and it ran and sounded awesome, good but not cheap. After much time and use it needed looking at so i took it off and went round AMD four wheel drive in merrylees, leicestershire plonked it on the counter and said, Recognize anything ? and low and behold it was near enough identical to the middle section on a 300tdi 90. So a bit of cutting here and welding there and i had a new system wich ran fine ( i use su s they are so easy to adjust and fettle) for a tenth of the price ! Happy days and good luck.