I really can't believe that the snorkel is really your problem:

1) Eextensive and oft repeated discussions on this forum have verified (some by engineers with actual empirical measurements of pressure gradients) that the intake (up to the throttle body) offers negligible restriction to the flow of air, given the moderate air flow requirements of a 2.3 liter engine. Any real restriction is at the throttle body and beyond (i.e., the intake manifold).

2) Only relying on the simple diamete measurements you made can be misleading. Any reasonably well engineered intake (and exhaust, as well) system is tuned to optimize airflow, and this tuning would include the dimensions (i.e., lengths) of the component parts -- such tuning includes figuring the standing waves created in the components. Occasionally, changing these lengths (as you did by shortening the snorkel) can actually create flat spots or underpowered portions along the rpm range when the standing waves create interference patterns or do not fit the components.

3) And lastly, the snorkel is designed with an opening pointing backwards (opening facing the radiator/bulkhead, rather than facing forward) to prevent a serious rainstorm from dumping water directly into the mouth of the snorkel.

I think you should look for other solutions, such as a clogged catalytic converter, etc.