GM 6.0 issues

[The Snowman]

I bought an older S&N Bravo 2 buggy in the spring of last year. It runs really well for 15ish minutes, tons of power, then loses quite a bit of power and loads up. After it sits for a few minutes I can fire it up and run another 15ish minutes before it does it again. I’m not an engine guy at all.
I had a few local guys look at it and we fixed a vacuum leak, changed out lots of parts. Fuel pump, fuel regulator, all new injectors, MAF, and Map sensors, throttle body etc.
It’s gotten better but still not great.
Trying to find a tuner anywhere within a few hours of Midwest Indiana. Original build said Hinson Motorsports did the tune.
Any suggestions?

 

[JohnnyJ]

What EFI are you using?

 

[The Snowman]

I have little info on the engine from the previous owner. Original build said 2006 LQ4, gmpp hot cam with LS6 springs, -6AN flow through files rails. LS6 intake. Tuned stock computer.

 

[Keith]

Fuel tank not venting properly?

 

[mobil1syn]

Fuel tank not venting properly?

that seems very likely.

The Snowman get a fuel pressure gauge

 

[crispins]

that seems very likely.

The Snowman get a fuel pressure gauge

I had a buggy and it has a similar issue.

What I figured out finally was I was getting vapor lock after running for about 30 mins or so.

If it sat for a bit it would start back up and run again for a while.

I ended up changing the fuel return location to the tank and I think the regulator and it was fine from then on till I sold it

 

[KacksterK5]

Sounds vapor lock like to me. Get a temp gun on the fuel rails and returns.

 

[The Snowman]

The fuel regulator has a gauge on it. It's under the hood though so I can't see it while driving. I'll have to check it next time it starts acting up.
It did have a really long looping hose on the tank vent so I just removed it and just left the 90 coming out the top of the cell. Too it out for 45 minuted and seemed to run really well. Hoping it was something that simple.
When I get more time this weekend I'll run it longer and see how it does.
Thanks for he help so far.

 

[mobil1syn]

if it does it again, before doing anything open the fuel cap and observe.

 

[YJ4Rox]

Also check your fuel line routing **** gets tight in a buggy.
the fuel line could be too close to the exhaust somewhere causing the fuel to boil.