The story happened to me one really hot summer about five years ago. (2)
It's probably the worst thing that's ever happened to me while driving a car. (See note 1)
I had bought/bought my car the week before and was still feeling/still felt very excited.(See note 2)
Imagine how the preterite would sound at this point: (3)“I bought my car the week before and…” Before what?
The reader’s thoughts are at this moment at the speaker’s time of utterance, because the main clause (2) is set in the speaker’s present. The past perfect tense in (3) marks the speaker’s effort to refer you back to the first sentence in the story, which is in the past tense. The past perfect tense is ALWAYS a relative tense; it never established a new temporal domain. Here the past perfect invokes the due subordination of the event “I-buy-car” to the situation “the story happened ...five years ago.”
The answer here is: past perfect is the right tense here.
But…If you removed from the story the second sentence marked (2), the temporal adverbial in (3) would set the sequence of events strait without resorting to the past perfect, and the simple past would do the job.
Note 2. was still feeling?/still felt?
The continuous tense form, in addition to other functions it serves, is a stativizer: it takes a verb (any verb) and makes a state out of it. You might say that the verb “feel” is a stative verb to start with, which is true. But the power of the progressive is enough to change that: it transforms the stative verb root “feel” into a dynamic verb when it is in the progressive form. That’s why I would say “I am feeling exited” when I really, really am, perhaps temporarily but truly, whereas “I am/feel excited” would mean much less about my... well.. excitement.
What can be more exciting than a brand new car? A brand new house? Nah. A brand new wife?
Go for “I was still feeling.”