The Simmons 4-1 sucks.

The exhaust system looks high quality, but it's 2", the stock size. On 140 B20E cars it is 2.125", there is no way Volvo used one size large pipe unless they had too.

Until you get a very professionally ported head, big cam & twin 45DCOE's, there is no gain in changing the exhaust manifold. Here is Australia it is easy & relatively cheap to get a custom exhaust, but in the USA, that is pricey.

I build my own. 2.25" for stock to mild, 2.5" for decent engings featuring decent Stahl style 4-1 & using Volvo style mufflers.

VPD has a very poor reputation, you pay money & 18 months latter still have nothing. Search this board & you will find horror stories of people sending a long motor + thousands of bucks, then getting nothing.

IPD stuff is severely overpriced.