I always say never to slowplay a straight, and of course here I do exactly that. Let's see if my reasoning is valid.

I limp in MP with QJs after the UTG limper. Two more limpers and both blinds play.

Flop comes pretty nice, TK9 rainbow giving me the nuts.

Blinds check and UTG who is short (started with 28) leads for 6 (pot is 12). Since I am directly behind him I decide to just call. The other stacks are between 168 and 400, I have them covered. Two people behind me calls, nobody raises.

Turn is a 2, completing the rainbow.

UTG leads for 6 again. Ok, no raise on the flop so I guess I can't expect a raise now. UTG has 14 left, so I miniraise. This means that if he pushes he will re-open the betting. Any larger raise would not let me re-open if he pushes.

One guy behind me calls (started with 168) and UTG just calls (damnit).

Turn is a huge brick, 33, and UTG pushes for 8. I raise to 70.

Good attempt to trap or just FPS?

Easier to give advice, esp for hands like this, if you include the pot size at every stage. Otherwise we need to try to puzzle out those things.

The pot on the flop is 12 and effective stack sizes are 400. I understand the flat call on the flop, I guess. But I mean even the 2 calls you got only added 12 to the pot. You want a big pot here, start building it.

If I just called the flop, I definitely want to get some real money in by the turn. He bet 6 into ...what, 36? and you raised to 12?!? Don't count on him to raise for you. Raise pot and see if anybody wants to play. If not, oh well, you lost a potential 12 from someone who might have called behind you with not much. I don't care about the 12, I want a big hunk of somebody's 400.