X pipe or H pipe, again

BigBlockMopar said
But I updated everything in the exhaust; went up in size from 2-1/4" to 2-1/2",

The current system is too large for the 318 in the car at the moment, .

More like just right. My 302 ford system from Dynomax was 2.5".

I had 6 into 1 headers on my slant 6 with a 3" collector. Guess what size the rest of the single exit system was? Yup..3".

Why people feel the need for restriction in an exhaust system is beyond me. Tuning it is the key.