A new part number doesn't necessarily mean new tooling. However, you are correct in saying that it is a way to cut cost by not issuing a new part number. A new part number means:

- Entirely new release/approval cycle. That means going through design, release and QA stages (QA is extremely expensive in automotive industry). Remember auto industry is not the software industry, there is no "agile" - waterfall is king because once the product is released, it is infinitely more expensive to change it

- Recalling old part numbers and shipping new ones

- Even the cost of printing new labels and making new packing materials can be non-insignificant

That said, a change in part equals a new part number, period. So, this was very likely a coverup AND an improper cost-reduction exercise.

I agree with you.

I did happen to notice from pictures that these particular parts have the part number cast on to them, so new tooling may be required.

Ah yeah, good observation.

Doesnt this mean that the part manufacturer had to be in on the process and that it probably wasnt the first time?