I have a 91 with a 305 tbi that has been converted to tpi. So i still have the tbi heads cam manafolds and y pipe. Im trying to deside between 1 3/4 and 1 5/8 size primaries. When I put this in i also have a 3 inch cat and cut-out to go in with the headers.

Will I lose any power with the 1 3/4 inch compaired to what i have now. I do plain on puting a 350 in later. If I deside to go with the 1 5/8 how much more power will I have with the 305 and how much less will I have with the 350.

If someone has before and after times with slp headers that would be great thanks

They quoted me $805 to my door for coated, air, with the installtion kit for eather 1 3/4 or 1 5/8

 

Buy for your intended end product. In this case, 1-3/4" primaries.

With a stock TBI cam and stock TBI heads, power will be pitiful with those headers. But, you'll be ready when you finish the project with a properly-equiped 350 without having to buy another set of headers.

The 1-5/8" would probably be okay with the 350, but SLP doesn't recommend it - so, why do it?