Ventrillo

now let me ask this, with running a higher PSI at lets say 11-12, is it a good idea to get better heads and cams, or can the stock internals handle that?

Nice Pony

Stock internals can handle 11-12 PSI no problem on the 4.0 as long as you have a good tune. Lots of guys have been running 11-12PSI for a long time with turbo and centri systems. The current X-Charger is good for around 10-11psi and the TVS MP1900 upgrade version I am working on will esily make 12+ psi. I should have this running within a month.