I understand it need a good introduction but for now it seems to not be what I was thinking...

7015419 If you would be so kind as to elaboreate and explain how and why it isn't what you had expected, and what gave you ideas that you feel are not what the story is about?

If I have been misleading you, maybe I could correct the errors that gave you the wrong impression?

If it is the Title or the Descriptions, I would love to get e help to make it fit better with the story.

Otherwise, I would love to explain what is confusing you, if that is part of the reason.

7015745 Yeah, sorry, It's only, first of all, Scootaloo and Sweetie appear as a main characters but now they seem more as extras... With the valves I was thinking it was going to be a inflation story or something like that but now I'm not sure.

Your story is good don't worry about that.

Is it me or were there an unusual number of exclamation points? I can see Pinkie Pie shouting often but Rarity?

7015848

Scootaloo and Sweetie appear as a main characters but now they seem more as extras.

I list the characters that has a role to play.

With the valves I was thinking it was going to be a inflation story

That would be the most comon use of a valve. I like more unorthodox means and uses from time to time, while not all inflatin has to be vissually enlarged.

but now I'm not sure.

This is after all Pinkie Pie, and she isn't content with staying within the frame. While I guess it could have been hinted in the description?

7020312

Is it me or were there an unusual number of exclamation points?

There is just one Exclamation per spoken dialogue paragraph, unless the line ended with a question. Granted I have started to experiment with adding emphasis by adding exclamation within the paragraphs in a few stories lately.

I can see Pinkie Pie shouting often but Rarity?

Something I guess Pinkie Pie could do. Otherwise, I think the standard expectation for that is capitalization, while I guess I could be wrong on occasion. Pinkie Pie can be just as overwhelming a Drama Queen as Rarity, while she could be just as Planning and organized as Twilight Sparkle.