i just did the isr mod today and i used rubber couplings found in the plumbing section at a store. i was wondering, can the rubber melt? i wasted too much money on this 24 bucks for 2 couplers. are the automotive rubber couplers cheaper? the first two pics are from mine and the 3rd one is cyberman's. i don't know how he got that 2.5 inch intake hose over that 3 inch pvc pipe.

 

Typically automotive couplers are a thread reinforced silicone. But the plumbing rubber is not the same compound as any auto ones that are rubber.
I used the same couplers that you used on my saturn when I was 16 and they never melted or changed. You should be fine but keep an eye on it there is a lot more heat on those couplers then my 4cyl fwd

 

I'd be careful, I'm almost positive that plumbing rubber will release toxic fumes when heated well beyond normal conditions.

 

i checked out the coupler today after i drove about 30 mins and it was a little bit warm. i will have to find a place where they sell auto couplers., my local auto store dont carry them.

 

ok after driving for 2 days with the mod i dont feel any difference in power because i got used to it. but i went up a hill today which i can barely go up in 3rd but today i went up the hill accelerating in 3rd. pretty good mod for the buck.