HLOS after headswap

[unseenstang]

96 GT runs strong after headswap except for Hardware limited operation strategy (Limp mode) at around 4500 RPM. No codes thrown. We can ease past the problem with very mild acceleration but with hard accel or WOT engine shuts down into HLOS. Otherwise runs good in mild normal driving.
All sensors seem to be good, what's causing our mystery shut down?

Thanks for your responses in advance.

 

[Mac-man]

i just did my headswap, and have had no problems with mine(other than the fact i blew 3rd and 4th gear in my tranny). that is weird about your car doing that. my car pulls noticeably harder all the way to 6 grand. it would however be nice to know what the problem is with the gt just in case mine ever does that.

 

[unseenstang]

Our rear end is 373's too, we've been using the white speedo gear in the VSS to adjust for speedo and odometer, I wonder if that gear was stripped if the VSS would affect fuel when it sent bad info to the PCM?

 

[unseenstang]

In case you're interested

The problem turned out to be weak coil packs, which although new (purchased on Ebay) apparently factory seconds not properly marked or identified. Went with Motorsports coil packs and the spark was 10 times hotter and our problem went away. Wasn't HLOS or revlimiter afterall.

 

[dkshadow]

The problem turned out to be weak coil packs, which although new (purchased on Ebay) apparently factory seconds not properly marked or identified. Went with Motorsports coil packs and the spark was 10 times hotter and our problem went away. Wasn't HLOS or revlimiter afterall.