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Discussion Starter · #1 ·
So am currently in the process of getting everything for a 3800 top swap on my 2004 Grand Prix GT, I have the pulleys and harmonic balancer I need, I also have a Gen3 M90 blower. My question is will it fit on my 04 after I get the lower for it or will I have to get a Gen5 blower? My motor is the L26 N/A, top swapping to an L32
 

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I'd suggest shopping for a Gen5 for a bit simpler swap. You won't need to adapt your 75mm electronic TB down to the Gen3's 69mm inlet (not to mention the slight performance/efficiency gain from the better inlet/outlet design). You're also able to use either LIM version, since an L67 LIM can be opened the ~3/4" to match the Gen5 outlet/gasket, but the L32 LIM can't go backwards and fill in that opening for the older design.

Since you're still in the parts collecting phase, I'd go for the optimal parts for this swap (L32 fuel rail, heads, etc.) while you're trying to prepare. It'll take time, but you'll be more content when the last bolt is torqued and ready to fire.

There's a bunch more you'll run into while doing the build, and especially getting the tune happy to run clean. 2004's with top-swaps are a bit picky with how to utilize boost, and we'd usually just leave the N/A tune on there with necessary changes to the fuel/air/spark tables that make it run happy. You'll get to that point eventually.
 

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Discussion Starter · #3 ·
I'd suggest shopping for a Gen5 for a bit simpler swap. You won't need to adapt your 75mm electronic TB down to the Gen3's 69mm inlet (not to mention the slight performance/efficiency gain from the better inlet/outlet design). You're also able to use either LIM version, since an L67 LIM can be opened the ~3/4" to match the Gen5 outlet/gasket, but the L32 LIM can't go backwards and fill in that opening for the older design.

Since you're still in the parts collecting phase, I'd go for the optimal parts for this swap (L32 fuel rail, heads, etc.) while you're trying to prepare. It'll take time, but you'll be more content when the last bolt is torqued and ready to fire.

There's a bunch more you'll run into while doing the build, and especially getting the tune happy to run clean. 2004's with top-swaps are a bit picky with how to utilize boost, and we'd usually just leave the N/A tune on there with necessary changes to the fuel/air/spark tables that make it run happy. You'll get to that point eventually.
So would the lower for an 03 GTP fit on the 04? There’s no reasonably priced Gen5 in my area so I’m just trying to make it work with the Gen3 if I can. I know there’s major downsides to it but it’d still make more power than stock. I’m already tuned with just an intake and exhaust.
 

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I've got a couple GenV's sitting around, if you're actually trying to buy one. The Gen3 LIM will work with about 15min of effort to match to Gen5 opening.

Just keep reading up, watching videos, etc. and get familiar with the details of the process. I usually spend days/weeks/months browsing and such before pulling the trigger on anything significant.

The tune will be totally out of whack when an M90 of either type gets installed. You have a 50% chance of it firing up, barely, and a 0% chance if it running properly once you start pushing the pedal. Tuning is a very overlooked necessity and skillset when doing upgrades beyond basic bolt-ons to these cars.
 
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