[CREWZIN]

Welcome to the forum. It sounds like you picked someone's PT that hasn't been properly taken care of. Yo haven't said what kind of mileage is on your PT but whatever it is, throw in some Platinum plugs gaped at.040in and a decent set of plug wires (not Chrysler OEM wires). Next thing is to have the transaxle flushed, not just drop the pan, flushed out with 16 new quarts of ATF+4.

There is no replacement upper manifold and throwing more TB's on won't do a darn thing and don't even think of adding that Throttle Body Spacer that you read about in magazines.

Yes, the low end pick-up does improve if you open up the air intake and if don't like the tube type, then modify the OEM air filter by replacing the filter with a more free flowing paper/cloth type and getting rid of any restrictions inside the filter itself. There's nothing wrong with the tube type if you stick with the K&N, Air-Raid or Volant filters. There's a Volant system for sale right now in the "for sale" section of the forum.

I can't tell you about the CAM stuff but if your going that far you might as well dump more money into the engine and hand it over to a machine shop.

Other things to do is run a few bottle of injector cleaner threw the fuel system and look around for a fee flow exhaust. It will reduce weight and let the engine work better.

I have a little under 100,000 miles, tube intake and Dyno Max exhaust. That's it for performance and it will chirp the front tires on the right roads and keep up with 99% of the rest of the cars on the road. Unless there's something wrong internally, yours should do the same with proper maintenance. The problem is that you don't know how the previous owner treated the cruiser.