you have lots of lift, and with the 1.6 rockers...wow.

as long as the valve train is not binding (check springs, read that to exceed .5 lift on vortec you needed different springs...) you are OK.

Headers or cat(s)? After cat system or is everything sotck?

An engine is an air pump - the more air you can pump through it the better.

You could try a pass with the vac line off the fule pressure regulator - it will allow slightly more fuel. If the cam has changed and the injectors/chip have not, youare probably starving for fuel on the top end.

Don't know limits of TPI system, but yes, long small diam runners (on any intake for that matter) are engineered for low rpm usage. High RPM want short runs that are large in diameter. Some intaked have been tried that have siamesed runners - 2 small diam that toghether make one large one to try and get best of both worlds.

What are you running for air cleaner/snorkel, etc? ON camaros vs firebird from best to worst design can mean 20+ HP! Now you gonna ask which is best, aren't ya? I can look that up, but Car CRaft did an article on TPI not too long ago.