Timing can help, an intercooler will help too. You already cleaned up the exhaust, but you might be able to improve on the intake side. Any restrictions are your enemies.
My truck had the real crappy banks box that didnt seal good, used crappy filters, etc. I finally found an ATS intake snail, found the orings for it and welded up an aluminum pipe into a 90 to make it work with my banks. I welded up a couple arms to a 4 inch exhaust pipe and mounted a cone filter and 90 degree reducing silicone boot to the turbo, then I eventually upgrading to a big filter and prefilter bag. I ditched the air dam thing that goes by the radiator to get fresher air, its pulling some heat but the less restrictive intake added power and lowered EGT very much, if i ever feel like it i may extend the intake to in front of the radiator, but an intercooler would be better in my opinion. Now the Turbo spools faster as a result. Plus I can work on the damn engine now without pulling that crap off. I also ceramic coated the exhaust all the way to the down pipe, turbo hot side, the wye thing, and the exhaust manifolds so under hood temperature was dramatically reduced, keeping that heat in will drive the turbo harder, meaning more responsive and efficient. Used to start steaming and melting snow after warming up, now I can keep a sheet of snow on the hood all day. I didn't do a before and after, but I have bumped the exhaust before and after and it went from bad burn territory to being able to touch it for a few seconds right after shutting it down. It'll flake off eventually I'm sure, but it's less damaging to the pipes than wrapping it in my opinion.
You can use methanol and/or water injection in the intake for added power AND cooling, but then you are reliant on that and if your dancing on 1150 on a grade with them and run dry.... no good. Someone hydrolocked their IDI before running wayyyy too much, but it cleans up soot too. The limiting factor with these engines has always primarily been fuel, so adding fuel to the air is one way to get more power. Propane used to be more popular but doesn't provide the cooling really. NOS isn't a fuel, it's an oxidizer, but if you're rolling coal it'll still help.... the other main weak point is the heads lifting above 10psi, unless you stud them down hard.
These old engines are using an N/A camshaft, I don't know how much valve overlap we get or anything, but there are a few different cams in the world now that usually add power. Obviously swapping cams is harder than turning a screw or pump!
Ambient air temperature will have an effect on pyro, not huge but it is noticable especially in areas with hot summer's and cold winters. If you're at 1150 in the winter, might not want to dial it up.