This weekend towing 21,000 gross,I saw 1200 degrees max @ 27 lbs boost. I'm not going to change anything. And that is with a HY35.
I have to admit, the upgrades that were installed this winter really made the truck come to alive while pulling.

 

My friend bought a Adkins built hybrid 35 and I have seen him hit 50 psi of boost and it has helped clear out a lot off his smoke that he had with the stock 35.
DM01

 

When I put the comp on, it lowered my EGT's by about 150*. When I was running just a scotty 2 w/hole and straight pipe, I could hit 1250*. With the comp in EZ mode, scotty, and exhaust, I could only hit 950*. It doesn't sound like you've got a boost leak. Having the extra boost would help lower EGT's but you don't want to up the boost without some type of boost fooler.

 

Researching on twins and found this post, so I figure I would up date it...... When I had 1150 EGTs on my old setup, I pulled the stock air filter The minder was only 60ish% used. Threw in the SII with the cowl hole, EGT's would barely hit 1000 I dont even think I hit 1100 empty since then.

 

just last week on my 12v i went from the banks housing on the stock hx35 to the Piers hybrid and i LOVE it! I kept the banks 14cm wg housing on the hybrid and that thing is GREAT compared to the stock. the compressor wheel is about an 1/8" bigger diameter at the center. dropped my egt about 100 degrees and pulls more better the injectors are stock as far as i know, has the banks fuel plate, don't know anything about how that particular plate though. i've got a little less smoke too since the swap.

the way the guy i talked to at piers described it, the stock hx35 will go to 35 psi but really isn't efficient after about 25psi. anyway, for mild power the hybrid 35/40 is a great way to go from my experience, spools to 32 real quick and keeps it nice and cool. the hybrid starts making a very noticeable difference above 12-15 psi.

if you're going to step up to anything bigger than that you might as well get twins

 

Depending on the fueling level of the truck, a hybrid 35 can peg a 50 psi gauge - not that it's good to do that. I can't imagine the drive pressures the head would see. When I put mine on a few years ago, Paul at HTT suggested to run it around 44 psi - much higher would put it out of the efficiency of the compressor housing.