Muffler or NOT

OK guys I'm almost road ready with the turbo 6 and I'm wondering what to do with my downpipe exhaust ill be running 3 inch from the exhaust housing and reducing it down to 2.5 back to the bumper I was wondering if I'm going to need some back pressure present in the system like a muffler or cherry bomb or if the reduction in pipe size well do the trick

Also about how long of the three inch pipe should I run before I reduce it down or should I run straight 3 inch back

This is going to be mostly track car but will see some road time I'm planning on running boost levels in the upper twenties to lower thirties also I'm running a 44 mm wastegate one more thing that may play into the equation is the exhaust housing itself
I'm getting a different turbo a pte6262 DBB and I'm Alittle bit undecided weather to go with 58 or 68 ar exhaust housing
The 58 should do the trick it should spool fast and hard but I'm bit concerned about top end but all the research I've read this turbo starts making boost at about 2200 rpm and peaks out but still makes power thru 5500 rpms the dyno numbers I seen on this turbo were taking with a 63 ar housing but that housing was a t3 I'm working with a t4 flange
What do you guys think