ls4 engine mount, throttle body spacer.
 

engine mount flip:
1: romove the dog bone by un bolting it from the engine and mount on core support. they are 15mm.
2: reinsert bolt into mount on core support. tighten it hard. rock it back and forth whil spraing wd40 inbetween it and metal bracket.
3: using 2 15mm whrenches put both on each end. turn them both at the same time towrd the engine.
4: if its not moving you did not lube it up enough.
5: once the rubber mount has the solid end of it towards the engine re insert dog bone.

throttle body spacer:
1 remove air intake tube. if its k&n just loosen all the clamps and disassemble it.
2 loosen the 4 10mm bolts holding the throttle body on.
3 set back the throttle body and insert gasket into spacer(provided)
4 using the supplied 10mm bolts insert one through the throttle body and spacer. start the threads.
5 there is a plug going towards the fire wall that will be in the way. they well move.
6 insert the remaining 3 bolts tighten one corner. then the opposite corner. then repeat.
7 reinstall intake. and enjoi

What do these mods accomplish, exactly? Rather, why would i do them?

Mount flips are common because the stock mount the way it is aligned allows for more engine movement (so you feel less vibrations, but can lose a HP or 2 in the movement) when you flip it, you make the harder sides take the place of the softer sides so that the engine moves a little less, freeing up that HP.

TB Spacers are just a waste of money. Supposed to add more room for air, but not worth it.

Butt dyno's over on ls1tech have said otherwise.
http://www.ls1tech.com/forums/ls4-fr...le+body+spacer

Oh yeah?

So they work for you LS4 guys? That's great to hear :)

Yeah, seems strange. I've read exactly what you're talking about too. But, from what I've read, because our intake is so restrictive, the TBS actually really improves the flow and amount of air going in. At least that's the theory.

What is a good TBS for the LS4 motor?

Read the link that Rick posted

Totally missed that. THanks.

i know this is an old thread...but i put an Airaid TBS on my car tonight took a video of the whistle noise it makes(not the best video but will kinda give you the idea) for those 7th gen owners that have been wanting one

YouTube - ‪2007 monte carlo ss throttle body spacer install‬‏