A rollover to a Roth IRA from a 401(k) or similar qualified retirement plan will almost always be partially, if not entirely taxable, so, if a distribution from the 401(k) is permitted, rollover to a Roth IRA is a reasonable way to increase taxable income. If the distribution is not permitted from the plan, perhaps the plan allows In-plan Roth Rollovers that are not subject to the same distribution restrictions as a rollover to a Roth IRA would have.
Regardless of the amount of balance or basis in traditional IRAs, conversion to Roth of up to the amount that it increases tax liability that would be covered by the otherwise unused EV tax credit ALWAYS makes sense (except in the case where the resulting increase in AGI has an effect on something other than the income tax, such as Medicare IRMAA).
