Where's my boost?

[-Alex-]

Finally got around to installing 16cm exh housing. The delayed spoolup in around town driving not as bad as I expected, but where did my boost go? On my first outing towing my 8k trailer to the mountains, I could barely get up to about 26 psi (was 30 w/ 12cm), although the power was still there, just more smoke. Is this normal? EGT didn't drop as much as expected, it will max out at 1250 deg instead of 1300, until the RPMs go over ~2400 and then I have to back off it to keep it in the safe area. Do I need to add more fuel to bring the boost back up?