Terrified rat during intros

I've been doing intros with my boys for a while now and I'm not getting anywhere. I have two groups (three adults only one intact who is jasper and two younger intact rats of which puffin is fourish months old) and most of them get along fine in neutral territory, but Jasper and Puffin have kind of stalled everything.

Puffin has been bitten a few times by Jasper (first time doing intro errors...) and is very very tense when ever he is around him. Jasper likes to side kick puffin (I try to prevent this) and shoves his head under him. Puffin also runs away from Jasper and that gets Jasper very excited and he chases the other rat.

I'm not sure what to do to help them get along, does anyone have advice?

Where are you doing intros? I like to use a table top with nothing on it, no toys, no boxes, nothing except a dish of yummy wet food. I like to use baby cereal or mushed up bananas.

That's where I am. I've been doing it for more than two weeks for as long as possible each night. There haven't been many fights, but The young male hasn't relaxed at all and the dominate male still reacts to him.

Do they have a set place for out time? I would move the intro from neutral area to familiar area. See how that works out. But be ready to intervene and grab the newbie(s) out of there in case something goes too tense.

Well I tried the bare play area tonight and it was interesting. Most of the rats got along fine (slightly more puffing and sniffing but no fights) but Puffin and Jasper still didn't get along. They were 'okay' standing off until Puffin runs away and then Jasper chases him. Some fur flew, and jasper got a small bite on his back foot (very very minor). By the end of around a half hour they were all a bit tense so I gave them some baby food immediately before bringing them to their cages and giving them a treat. I have them out in my bathroom and I switch cages every day.

I'm thinking about bringing back the vanilla for next time? How do you think that went? I'm just not sure what to do with the running away.

I did another intro today and everyone was fine except jasper. I mean they postured and puffed but thats standard for intro. I'm not sure how Jasper did because he fell off a level in his cage and his foot is swollen and painful so he sat on my lap or behind the toilet mostly. (He got advil after, and is in a place with easy access to food and water)

Puffin was still scared of him even though Jasper was very limpy and sad. *throws hands into air* will the scaredness go away over time?

Sounds like your intros are progressing normally. Except for the booboo with Jasper. Poor little guy but in a way, it worked in Puffin's favour. We hope that Puffin stops being scared but that could be part of his personality.