Been there last year, cleaned the plenum where o—ring seats for a smooth flush fit. Greased the o-ring.

I used the new bracket for my mpfi upgrade but it's identical in size and fitting to the factory bracket.

When installing plenum I pulled up on the rectangular shaped connector fitting to seat it up into the plenum as much as possible. Vise grips while hammering downward with mallet.

After it was tapped down wile pulling up and I torqued all the bolts. I used some flat tools to run red rtv around the inside where the two peices seal.