Oh crap! Let me get out my HP calculator.
First you can't start off basing things off of the factory rating. I've seen LS1 4th gens make between 285-320ish whp for the M6 SLP optioned ones. Most are 300-310. A firehawk is a SLP optioned fbody. The Firehawk came with a 3" dual out the left or dual dual SLP catback. It also should have came with the blackwing airlid. 2 more reasons why you can't add those to the stock HP rating. If you have the silencers and the lid doesn't say SLP, you got screwed with a stock LS1 lid someone put on. Yes a lid does generally make 8-10hp. A lide without the ribs doesn't make yours an aftermarket design with improved flow characteristics. Maybe 3-5 hp if anything for the modded stocker. Your only real addition are headers. The effetiveness of a handheld is very debatable. So with an A4, I'll speculate 335 at the wheels on a dynojet. Add 18% for bhp. And I'll say stop cutting corners on your mods if you really care about HP, and don't worry about driving it hard. The things were made to drive. It won't be a collectors items for 20 or more years, if ever. It already sounds like it is missing the SLP options so its collector value has decline. Might as well enjoy it. My wife daily drives a car that only 1829 were made for half a year, and hers is a even more rare M6. Drive the car and enjoy it!!!
First you can't start off basing things off of the factory rating. I've seen LS1 4th gens make between 285-320ish whp for the M6 SLP optioned ones. Most are 300-310. A firehawk is a SLP optioned fbody. The Firehawk came with a 3" dual out the left or dual dual SLP catback. It also should have came with the blackwing airlid. 2 more reasons why you can't add those to the stock HP rating. If you have the silencers and the lid doesn't say SLP, you got screwed with a stock LS1 lid someone put on. Yes a lid does generally make 8-10hp. A lide without the ribs doesn't make yours an aftermarket design with improved flow characteristics. Maybe 3-5 hp if anything for the modded stocker. Your only real addition are headers. The effetiveness of a handheld is very debatable. So with an A4, I'll speculate 335 at the wheels on a dynojet. Add 18% for bhp. And I'll say stop cutting corners on your mods if you really care about HP, and don't worry about driving it hard. The things were made to drive. It won't be a collectors items for 20 or more years, if ever. It already sounds like it is missing the SLP options so its collector value has decline. Might as well enjoy it. My wife daily drives a car that only 1829 were made for half a year, and hers is a even more rare M6. Drive the car and enjoy it!!!
